14-733C2
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`COLLISION MONITORING SYSTEM
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`5
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`CROSS REFERENCE TO RELATED APPLICATIONS:
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`The present application is a continuation-in-part of application serial no.
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`09/562,986 filed May 1, 2000 which is a continuation-in-part of application serial
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`number 08/736,786 to Boisvert et al. which was filed on October 25, 1996, now
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`1 0 US patent no. 6,064,165 which was a continuation of united States application
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`serial number 08/275,107 to Boisvert et al. which was filed on July 14, 1994
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`which is a continuation in part of application serial number 07/872,190 filed April
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`22, 1992 to Washeleski et al., now United States patent 5,334,876. These
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`related applications are incorporated herein by reference. Applicants also
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`15
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`incorporate by reference United States patent number 5,952,801 to Boisvert et
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`al, which issued September 14, 1999. This application also claims priority from
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`United States Provisional application serial no. 60/169,061 filed December 6,
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`1999 which is also incorporated herein by reference.
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`20
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`FIELD OF THE INVENTION:
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`The present invention concerns motor driven actuator control systems and
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`methods whereby empirically characterized actuation operation parameters are
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`subsequently monitored.
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`25
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`BACKGROUND:
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`National Highway Traffic Safety Administration (NHTSA) Standard 118
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`contains regulations to assure safe operation of power-operated windows and
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`roof panels.
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`It establishes requirements for power window control systems
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`located on the vehicle exterior and for remote control devices. The purpose of
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`30
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`the standard is to reduce the risk of personal injury that could result if a limb
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`catches between a closing power operated window and its window frame.
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`Standard 118 states that maximum allowable obstacle interference force during
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`1
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`an automatic closure is less than 1 00 Newton onto a solid cylinder having a
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`diameter from 4 millimeters to 200 millimeters.
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`Certain technical difficulties exist with operation of prior art automatic
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`power window controls. One difficulty is undesirable shutdown of the power
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`5 window control for causes other than true obstacle detection. Detection of
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`obstacles during startup energization, soft obstacle detection, and hard obstacle
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`detection each present technical challenges requiring multiple simultaneous
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`obstacle detection techniques. Additionally, the gasket area of the window that
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`seals to avoid water seepage into the vehicle presents a difficulty to the design of
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`10
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`a power window control, since the window panel encounters significantly different
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`resistance to movement in this region. Operation under varying power supply
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`voltage results in actuator speed variations that result in increased obstacle
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`detection thresholds.
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`15
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`SUMMARY OF THE INVENTION:
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`This invention concerns an improved actuator system that provides faster
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`operation, more sensitive obstacle detection, faster actuator stopping with
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`reduced pinch force, and reduced false obstacle detection all with less costly
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`hardware. This invention has utilization potential for diverse automatic powered
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`20
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`actuator applications including positioning of doors, windows, sliding panels,
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`seats, control pedals, steering wheels, aerodynamic controls, hydrodynamic
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`controls, and much more. One exemplary embodiment of primary emphasis for
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`this disclosure concerns an automatic powered actuator as a motor vehicle
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`sunroof panel.
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`25
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`An exemplary system built in accordance with one embodiment of the
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`invention implements position and speed sensing is via electronic motor current
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`commutation pulse sensing of the drive motor. Motor current commutation pulse
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`counting detection means and counting correction routines provide improved
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`position and speed accuracy.
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`30
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`In
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`one
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`exemplary
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`embodiment,
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`stored
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`empirical
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`parameter
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`characterizations and algorithms adaptively modify obstacle detection thresholds
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`2
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`during an ongoing actuation for improved obstacle detection sensitivity and
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`thresholds resulting in quicker obstacle detection with lower initial force, lower
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`final pinch force and reduced occurrences of false obstacle detection.
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`An exemplary embodiment of the collision sensing system uses a memory
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`5
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`for actuation speed measurement, motor current measurement, and calculations
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`of an ongoing actuation with real time adaptive algorithms enables real time
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`running adaptive compensation of obstacle detection thresholds.
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`BRIEF DESCRIPTIONS OF THE DRAWINGS:
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`1 0
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`Figure 1 is a block diagram schematic of the components of an exemplary
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`embodiment of the present invention;
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`Figures 2A- 2D are schematics of circuitry for controlling movement and
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`sensing obstructions of a motor driven panel such as a motor vehicle sunroof;
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`Figure 3A is a plan view depicting an optical sensing system for
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`15 monitoring an obstruction in the pinch zone of a moving panel such as a motor
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`vehicle sunroof;
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`Figure 3B is a front elevation view of the Figure 3A optical sensing
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`system;
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`Figure 3C is a plan view depicting an optical system with moving optics for
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`20 monitoring an obstruction at the leading edge of a moving panel such as a motor
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`vehicle sunroof;
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`Figure 3D is a front elevation view of the Figure 3C optical sensing
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`system;
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`Figure 3E is a plan view depicting an optical sensing system with moving
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`25
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`optics, flexible optic fiber, remote IR emission, and remote IR detection for
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`monitoring an obstruction at the leading edge of a moving panel such as a motor
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`vehicle sunroof;
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`Figure 4 represents typical startup energization characteristics of motor
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`current and per speed versus time;
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`30
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`Figure 5 represents a simplified example of characteristic steady state
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`nominal motor operation function versus time or position;
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`3
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`Figure 6 represents a simplified example characteristic dynamic transient
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`motor operation function versus time and/or position showing motor operation
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`function with transients;
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`Figure 7 represents a simplified example characteristic dynamic periodic
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`5
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`cyclic motor operation function versus time and/or position showing motor
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`operation function with cyclic disturbances; and
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`Figure 8 is a sequence of measurements taken by a controller during
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`successive time intervals and operation of a monitored panel drive motor.
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`10
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`BEST MODE FOR PRACTICING THE INVENTION:
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`Figure 1 shows a functional block diagram of an actuator safety feedback
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`control system 1 for monitoring and controlling movement of a motor driven panel
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`such as a motor vehicle sunroof. A panel movement controller 2 includes a
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`commercially available multipurpose microcontroller IC (integrated circuit) with
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`15
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`internal and/or external FIFO memory and/or RAM (Random Access Memory) 2a
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`and ADC (analog-to-digital-converter) 2b.
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`Eight-bit word bytes, eight-bit counters, and eight-bit analog-to-digital
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`conversions are used with the exemplary controller 2.
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`It should be fully realized,
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`however, that alternative word lengths may be more appropriate for systems
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`20
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`requiring different parameter resolution. Larger word bytes with equivalent ADC
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`resolution enables greater resolution for motor current sensing. Likewise, larger
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`word bytes with higher microcontroller clock speeds enable greater resolution for
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`motor per speed sensing plus quicker digital signal processing and algorithm
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`processing for quicker response time.
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`25
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`A temperature sensor 3 (which according to the preferred embodiment of
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`the invention is an option) when installed, is driven by and sensed by the
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`controller 2. Temperature sensing allows the panel controller 2 to automatically
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`sense vehicle cabin temperature and open or close the sunroof to help maintain
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`a desired range of temperatures.
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`Temperature compensation of actuator
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`30
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`obstacle detection thresholds is typically unnecessary.
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`4
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`

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`An optional rain sensor 4 can be both driven by and sensed by the
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`microcontroller 2. Automatic closing of the sunroof panel occurs when the
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`sensor is wet. Subsequently, the sunroof panel can be opened when either
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`falling rain has stopped for some time duration or when the rain has evaporated
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`5
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`to some extent.
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`Manual switch inputs 5 are the means by which operator control of the
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`system occurs.
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`Limit switch inputs 6 indicate to the control system such physical inputs as
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`HOME position, VENT/NOT OPEN Quadrant Switch, and end of panel
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`10 movement. Limit switch signals indicate where microcontroller encoder pulse
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`counter registers are set or reset representative of specific panel position(s).
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`Motor drive outputs ?a and 7b control whether the motor drives the panel
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`in the forward or the reverse direction. When neither the forward nor the reverse
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`direction are driven, the motor drive terminals are electrically shorted together,
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`15
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`possibly via a circuit node such as COMMON, resulting in an electrical loading
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`and thus a dynamic braking effect.
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`Motor plugging drive, which is the application of reverse drive polarity
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`while a motor is still rotating, is an optional method of more quickly stopping the
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`motor, but has been unnecessary for use with the preferred embodiment of the
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`20
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`sunroof panel controller due
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`to satisfactory performance
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`taught by
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`this
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`disclosure. Very large motor plugging currents are often undesirable because
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`they can easily exceed typical maximum stalled rotor currents producing
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`undesired motor heating in large applications. Such high motor plugging currents
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`can be detrimental to the life and reliability of electromechanical relay contacts
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`25
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`and solid state switches used to switch motor operating currents. High motor
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`plugging currents can also cause undesirable transients, trip breakers, and blow
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`fuses in a power supply system.
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`Application of brakes and/or clutches is also unnecessary with the
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`automotive sunroof system due to the improved real time obstacle detection
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`30
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`performance taught by this disclosure.
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`5
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`

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`Optical Obstacle Detection
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`Obstacle detection by actual physical contact and/or pinch force with
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`human subjects is somewhat unnerving to some individuals. For improved
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`system safety and user comfort, the preferred system utilizes non-contact
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`5
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`detection of obstacles in the path of the moving panel. Of various technologies
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`by which it is possible to sense an obstacle without physical contact, I R (infrared)
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`emission with transmission interruption mode detection is preferred.
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`I R emitting
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`diodes and/or IR laser diodes are the two preferred IR emission sources.
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`IR
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`photodiodes and/or I R phototransistors are the two preferred I R detection means.
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`1 0 Optical obstacle detection senses and enables stopping of
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`the actuator
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`movement prior to significant applied pinch force and possibly prior to actual
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`physical contact with a subject.
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`In unusual light conditions, explained below,
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`optical sensing means becomes temporarily ineffective, thus obstacle detection
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`via motor current sensing or current sensing and speed sensing means becomes
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`15
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`the remaining reliable backup method of detecting an obstacle.
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`Of two preferred configurations utilized for implementing I R transmission
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`interruption mode of obstacle detection, the first is use of at least one emitter and
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`at least one detector sensing at least across the pinch zone in close proximity to
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`an end of travel region of a sunroof. As shown in Figures 3A and 38, at least
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`20
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`one I R emitter 1 00 and at least one I R detector 1 02 are separated from each
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`other by a sunroof pinch zone 104.
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`In an exemplary embodiment of the
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`invention, opto sensing of obstructions is across and in relatively close proximity
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`to a pinch zone near the end of travel region of a sunroof. The depictions in
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`Figures 3A and 3B do not show the entire region between emitter and detector
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`25
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`but it is appreciated that a gap G between emitter and detector is on the order of
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`the width of the moving sunroof.
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`In this preferred embodiment, cabling 108
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`passes to the region of the detector 1 02 around the end of the sunroof liner in the
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`region of the end of the sunroof travel. The detector and emitter are fixed to the
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`sunroof liner and do not move.
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`Implementation of this fixed configuration is
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`30
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`simplified by lack of moving components, although the sunroof may have to push
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`the obstacle into a sensing field between the emitter 1 00 and the detector 1 02.
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`6
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`

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`Thus, although the sensing means is non-contact, the sunroof can still contact
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`the obstacle.
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`Of two preferred configurations utilized for implementing I R transmission
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`interruption obstacle detection, the second is use of at least one emitter and at
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`5
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`least one detector sensing at least immediately ahead of the front moving edge
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`of the moving portion of a sunroof. As shown in Figures 3C and 30, at least one
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`IR emitter 100 and at least one IR detector 102 are separated proximal a front
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`moving edge of a sunroof 103.
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`In an exemplary embodiment of the invention,
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`opto-sensing of obstructions is across and in relatively close proximity to a front
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`10
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`edge 105 of the sunroof 103. The depictions in Figures 3C and 30 show the
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`entire region between emitter and detector for which a gap G, between emitter
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`and detector, is on the order of the width of the moving sunroof. In this preferred
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`embodiment, flexible flat circuitry 107 passes to the emitter 100 and the detector
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`1 02 of the moving panel or window to the region of the front moving edge.
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`15 Alternate means to supply electrical signal and/or power to the moving opto(cid:173)
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`electronic components includes means such as electrical contact brushes
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`cooperating with conductive traces on the moving panel. Power and signal are
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`optionally both transmitted over the same conductors. Figure 3E shows an
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`alternative means to supply I R emission to receive I R detection from the front
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`20
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`edge of the moving panel via flexible moving optic fiber 303 means connected
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`with components 300, 302 that respectively emit IR and detect IR signals.
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`IR
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`optical fibers are terminated at each end to optical components 304, 305 that
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`perform collimating, reflecting, and
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`focusing requirements.
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`The structure
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`depicted in Figures 3A - 3E make it possible to sense obstructions with no
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`25
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`physical obstacle contact regardless of the position of the moving sunroof.
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`Alternate, non-preferred means of obstacle detection include sensing back
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`reflection from a reflective surface of radiation emitted from an emitter, electric
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`field sensing of proximal material dielectric properties, and magnetic field sensing
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`of proximal material inductive properties.
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`30
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`Various techniques improve the operation and reliability of non-contact
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`optical detection sensing.
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`In accordance with an exemplary embodiment of the
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`7
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`

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`present invention, the IR emitter 100 is driven with a duty cycle and frequency.
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`One typical automobile sunroof application uses 20% duty cycle at 500 Hz I R
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`emitter drive synchronized with IR detector sensing. Pulsed drive allows the IR
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`emitter 100 to be driven harder during its on time at a low average power. This
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`5
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`harder drive yields improved signal-to-noise for IR sensing by the IR detector.
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`The I R detector circuit synchronously compares the I R signal detected during I R
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`emitter on times with IR emitter off times to determine ambient IR levels for drive
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`and signal compensation purposes. This allows the I R emitter to I R detector
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`optical coupling to be determined with a level of accuracy and reliability using
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`1 0
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`closed loop feedback techniques.
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`Automatic gain feedback control techniques maintain the level of the I R
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`emitter drive and/or the gain of the I R detector circuit so that optical coupling is
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`above minimum desirable values. Such automatic gain compensates, within
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`certain
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`limitations,
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`factors
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`including decrease
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`in
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`IR emitter output over
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`15
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`accumulated time at temperature, IR emitter output temperature coefficient, dirt
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`and haze fouling optic components, and high ambient IR levels.
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`Highly directional I R optical lenses and/or aligned polarized filters on both
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`the I R emitter and I R detector maintain better optical coupling and reduce the
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`effects of ambient I R and reflected I R from other directions. Location of the I R
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`20
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`detector in a physical recess further reduces the possibility of extraneous I R
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`"noise" from affecting the optical coupling.
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`Despite various means to reduce the possibility of excess extraneous I R
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`from being detected, certain conditions occur that may allow very high levels of
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`direct and/or reflected sunlight to be "seen" by the detector. Sun IR power levels
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`25
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`can saturate the detector output signal level so that obstacle blockage of the
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`pulsed I R emitter signals is not reliably sensed. Under such unusual "white out"
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`circumstances, theIR optical system is disabled by the panel controller 2 until the
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`sunroof actuator is nearly closed , at which position ambient I R noise is shielded
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`by the sunroof. Thus, the complete emitter-detector I R coupling is made more
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`30
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`reliable for the last movement of pinch point closure. Complete body blockage of
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`the I R coupling path between the emitter and detector is not a "white out"
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`8
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`

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`condition, although if the body is blocking both ambient IR and emitted IR signal
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`at the detector, a "black out" condition is interpreted as an obstacle detection.
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`Although the IR obstacle detection means may be temporarily found to be
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`unreliable by high ambient levels of I R, the disclosed sensing of hard and/or soft
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`5
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`obstacles by motor current monitoring is always active as a redundant obstacle
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`detection means.
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`Detailed Schematic
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`The controller schematic shown in Figures 2A- 20 implements collision
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`1 0
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`sensing in one form by activating a light emitting diode 1 OOa which emits at
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`periodic intervals. In the event the infra red radiation is not sensed by a photo
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`transistor detector 1 02a, the controller 2 assumes an obstruction and
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`deactivates the sunroof motor M. There is also a redundant and more reliable
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`obstacle detection means for detecting obstacles based upon sensed motor
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`15
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`operation parameters.
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`The preferred controller 2 is an Atmel 8 Bit microprocessor having 8
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`Kilobytes of ROM and includes programming inputs 106 which can be coupled to
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`an external data source and used to reprogram the microprocessor controller 2.
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`User controlled inputs 5a, 5b are coupled to user activated switches which are
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`20
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`activated to control movement of the sunroof. The inputs are similar to now
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`issued Patent No. 5,952,801 to Boisvert et al, which describes the functionality of
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`those inputs. Limit switch outputs 5c, 5d, 5e are also monitored by the controller
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`2 and used to control activation of the sunroof drive motor.
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`The schematic depicts a clock oscillator 11 0 for providing a clock signal of
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`25
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`6 MHZ for driving the microprocessor controller 2. To the upper left of the
`oscillator is a decoupling capacitor circuit 112 for decoupling a vee power signal
`to the microprocessor.
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`The circuitry depicted in Figure 2B provides power signals in response to
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`input of a high signal at the ignition input 114. When the ignition input goes high,
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`30
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`this signal passes through a diode 116 to the base input 118 of a transistor 120
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`which turns on. When the transistor 120 turns on, a regulated output of 5 volts
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`9
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`

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`(VCC) is provided by a voltage regulator 122 in the upper right hand corner of
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`Figure 2B. A voltage input to the voltage regulator 122 is derived from two
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`battery inputs 124, 126 coupled through a filtering and reverse polarity protection
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`circuit 130. Immediately above the positive battery input 124 is a relay output
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`5
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`131 which provides a signal one diode drop less than battery voltage VBAT
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`which powers the relay coils 132, 134 (Figure 2D) for activating the motor.
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`The circuitry of Figures 2A- 2D includes a number of operational
`amplifiers which require higher voltage than the five volt vee logic circuitry
`power signal. At the extreme right hand side of the schematic of Figure 2B are
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`1 0
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`two transistors 136, 138 one of which includes a base 140 coupled to an output
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`142 from the microprocessor controller 2. The second transistor has its collector
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`coupled to the battery and an output on the emitter designated V-SW. When the
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`microprocessor turns on the transistor 138, the V-SW output goes to battery
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`voltage. The V-SW output is connected to a voltage regulator (not shown) which
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`15
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`generates a DC signal that is supplied throughout the circuit for operation of the
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`various operational amplifiers.
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`The microprocessor controller 2 also has two motor control outputs 150,
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`152 which control two switching transistors 154, 156 , which in turn energize two
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`relay coils 132, 134. The relay coils have contacts 162, 164 coupled across the
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`20 motor M for energizing the motor windings with a battery voltage VBAT. One or
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`the other of the transistors must be turned on in order to activate the motor.
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`When one of the two transistors is on, the motor M rotates to provide output
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`power at an output shaft for moving the sunroof or other panel along a path of
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`travel in one direction. To change the direction of the motor rotation, the first
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`25
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`transistor is turned off and the second activated. The motor used to drive the
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`sunroof panel back and forth along its path of travel in the exemplary
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`embodiment of the present invention is a DC motor.
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`Figure 2C depicts a circuit 180 for monitoring light emitting diode signals.
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`A light emitting diode 1 OOa has an anode connection 181 coupled to the V-
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`30
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`switched signal and the cathode is coupled through a switching transistor 182 to
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`a microprocessor output 183. The microprocessor outputs a 500 hertz signal at
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`10
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`

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`this output 183 having a 20% duty cycle to the base input of the transistor. When
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`the transistor turns on, the LED cathode is pulled low, causing the light emitting
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`diode 1 OOa to emit IRradiation. Under microprocessor control, the light emitting
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`diode produces a 500 hertz output which is sensed by a photo detector 1 02a. As
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`5
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`the light emitting diode pulses on and off at 500 hertz, the photo detector
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`responds to this input. When current flows in the photo detector, a voltage drop
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`is produced across a voltage divider 184 having an output coupled to an
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`operational amplifier 186. When current flows in the photo detector in response
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`to receipt of a light signal the voltage divider raises the voltage at the inverting
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`1 0
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`input 188 to the amplifier 186. The non-inverting input to this amplifier is
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`maintained at 2.5 volts by a regulated voltage divider 188. The operational
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`amplifier 186 and a second operational amplifier 190 define two inverting
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`amplifiers which in combination produce an output signal of 500 hertz. With no
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`signal appearing at the photo detector, an output 192 from the operational
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`15
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`amplifier 190 is 2.5 volts. This signal is coupled to the microprocessor controller
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`2. In response to receipt of the photo detector signal, this signal oscillates and
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`this oscillating signal in turn is sensed by the microprocessor.
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`The microprocessor controller 2 has two inputs 192, 194 that provide
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`input signals to a comparator implemented by the microprocessor controller. As
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`20
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`the state of the comparator changes, internal microprocessor interrupts are
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`generated which cause the microprocessor to execute certain functions. The first
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`input 192 is derived from the output from the phototransistor 1 02a. The second
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`input 194 to the comparator is a 3.3 volt signal generated by a voltage divider
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`195.
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`25
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`Motor current monitoring
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`A motor current monitoring circuit is depicted in Figure 20 and includes a
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`number of operational amplifiers 200- 203 coupled to a current measuring
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`resistor 210 in the lower right hand portion of the circuit diagram. This current
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`30 measuring resistor is coupled to the operational amplifier 200 configured as a
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`differential amplifier through a second resistor 211. An output 212 from this
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`11
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`

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`differential amplifier is a signal proportional to the current through the motor
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`windings which has been amplified by a factor of about four. The output from this
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`amplifier passes to a second gain of 3 amplifier 201 to an output 214 coupled to
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`the microprocessor controller through a resistor 215. This signal is monitored
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`5
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`by the microprocessor and converted by an A to D conversion to a digital value
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`directly related to motor current.
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`An input 220 to the second pair of operational amplifiers 202, 203 is either
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`an output from the first differential amplifier 200 or the second gain of 3 amplifier
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`201 depending upon whether a resistor 222 is installed in the circuit. One but not
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`1 0
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`both of the resistors 222, 223 are installed in the circuit.
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`The changing signal output from the resistor 210 is coupled to an inverting
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`input of an AC coupled amplifier and produces an output signal 226 to the
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`microprocessor controller 2 which changes with motor current and more
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`particularly as the commutator brushes pass over the motor armature
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`15
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`commutation segments , the signal changes to form a sequence of pulses. The
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`amplifier 203 is a level shifting amplifier which reduces the gain of the first
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`amplifier depending upon sensed conditions. When the motor first is activated a
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`large current rush occurs due to the fact that the motor is stalled. This large
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`current rush changes the output of the amplifier 203 thereby producing
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`20 meaningful data even in a high current situation. As the current changes, the
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`output of this top amplifier 203 varies to allow meaningful data to be supplied to
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`the microprocessor regardless of absolute values of motor current.
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`The signal at the microprocessor is a analog signal having the ripple
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`component as the motor rotates. This signal is in turn interpreted by the
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`25 microprocessor controller 2 which generates values directly related to motor
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`speed based upon the sensing and counting of these pulses. Additionally, the
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`value changes in such a way that the slope can be monitored so that the
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`microprocessor can use digital signal processing techniques on the input signal
`
`to determine a stalled motor condition representing an obstacle.
`
`30
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`At motor startup the large currents that are experienced make it difficult to
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`sense object collisions with the moving window or panel. In accordance with one
`
`12
`
`

`
`embodiment of the invention the controller maintains a position of the leading
`
`edge of the window or panel and during certain startups will alter a startup
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`sequence.
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`If the window or panel is stopped in a region where entrapment is more
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`5
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`likely, such as in the last portion of travel just before closing of the window or
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`panel, the motor is energized to move the window a short distance away from its
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`stopped position away from the closed position. A controller which controls the
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`motor then reverses motor rotation sense to move the window or panel in a
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`direction to close the window or panel. Stated another way, the controller causes
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`1 0
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`the motor to move the panel or window in a direction to open the window or panel
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`and then change motor energization to close the window or panel. This process
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`avoids difficult to sense obstacle detection during the initial start up period of
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`motor operation.
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`The region of the window or panel seal is a region of increased motor
`
`15
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`load. In this region, in accordance with one embodiment of the invention, in
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`response to a detection of an obstacle, the controller immediately causes motor
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`deenergization, followed by quick reversal of actuation drive for a short distance
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`(for example one inch). The controller then performs an immediate re(cid:173)
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`energization in the initial direction so that a more sensitive and accurate obstacle
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`20
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`detection process can be performed. The controller can either determine that the
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`initial obstacle detection was false due to actuator startup conditions, and thus
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`continue to power the motor or else verify the obstacle presence that was
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`previously detected and cause the appropriate response of stopping or
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`alternatively stopping and reversing the window or panel for a short distance.
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`25 Measured Motor Parameters - DC Current Sensing
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`By monitoring the two inputs 216, 226, the microprocessor controller 2
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`monitors the motor current from which the controller 2 determines both sunroof
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`incremental position and speed. Sensed motor current is always positive
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`regardless of motor drive polarity and rotation direction. For either condition of
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`30
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`drive polarity the non-energized side of the motor is connected to COMMON
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`13
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`

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`through the low value current sensing resistor 210 to produce a positive analog
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`signal voltage directly proportionate to the motor current.
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`This motor current signal is converted via hardware and/or software to a
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`filtered signal and scaled by a fixed or optionally variable reference voltage to
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`5
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`produce a value less than a determined maximum value where the following
`definition applies: CUR = {sensed motor current analog-to-digital-converted and
`scaled to engineering units}, where the analog value for motor current is
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`10
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`15
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`converted to eight-bit digital resolution via an eight-bit ADC (analog-to-digital
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`converter) within the microprocessor controller 2. Eight bit resolution in a
`controller counter for CUR yields an absolute count range of 0 s CUR s 255,
`where a maximum analog reference voltage is provided to the ADC to set the
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`anticipated maximum possible motor current limit value represented by a
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`reference value 255.
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`A preferred means to increase sensed motor current resolution and thus
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`improve obstacle detection sensitivity is to adaptively adjust the reference
`voltage (set = value of 255 representative of full scale) and/or the sensed motor
`current signal during times of relatively low current operation, returning to the
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`highest scale during starting energization, end-stall detection, and as necessary
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`for obstruction detection. For this eight-bit example, at least one bit of current
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`20 measurement resolution can be gained during
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`low current operation by
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`decreasing the reference voltage by such means as a variable attenuation
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`network and/or by scaling up the motor current signal by such means as a
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`variable gain amplifier.
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`Analog motor current signal is lowpass filtered to remove noises from
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`25 motor current commutation and switching transients to produce a fast running
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`average analog drive current signal to the microcontroller representative of motor
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`torque load conditions. This voltage signal is converted to a scaled digital value
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`by the microprocessor. For example, normal steady operation of the motor at
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`low battery voltage causes
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`the controller
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`to
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`register a digital value of
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`30
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`approximately 80 of full scale 255, whereas startup energization at high battery
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`voltage will result in a peak digital value of approximately 240 of full scale 255.
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`14
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`

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`Measured Motor Parameters - AC Current Sensing
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`Typical DC brush motor current signals also have inherent waveform AC
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`ripples due to rotor current commutation. These motor current pulses directly
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`5
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`relate to
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`incremental rotation of the motor shaft and since gears and/or
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`mechanical drive linkages link the shaft to the moving window or panel, directly
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`relate to incremental change of position of the actuator. The relationship of
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`motor current commutation pulses to actuator incremental motion
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`is not
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`necessarily a linear correspondence.
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`1 0
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`Motor current analog signal can be AC coupled, bandpass filtered,
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`amplified, and compared with a threshold to produce a digital signal via an input
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`representative of motor current commutation signals. Alternatively, motor current
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`commutation signals can be directly sensed from the motor current signal via
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`ADC and digital signal processing bandpass filtering having sufficient resolution
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`15
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`to accurately measure the relatively lower amplitude waveforms characteristic of
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`motor current commutation pulses.
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`Various alternative and more expensive incremental encoder, absolute
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`encoder, and resolver means can produce similar signals representative of
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`incremental or absolute motor rotor position.
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`20
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`A