Paper No. ________
`
`UNITED STATES PATENT AND TRADEMARK OFFICE
`_______________
`
`BEFORE THE PATENT TRIAL AND APPEAL BOARD
`_____________
`
`MICRO MOTION, INC.
`Petitioner
`v.
`
`INVENSYS SYSTEMS, INC.
`Patent Owner
`
`Patent No. 7,571,062
`Issue Date: August 4, 2009
`Title: DIGITAL FLOWMETER
`_______________
`
`Inter Partes Review No. Unassigned
`____________________________________________________________
`
`DECLARATION OF DR. MICHAEL D. SIDMAN
`
`4812-2280-4248.1
`
`1
`
`Micro Motion 1002
`
`
`
`UNITED STATES PATENT AND TRADEMARK OFFICE
`_______________
`
`BEFORE THE PATENT TRIAL AND APPEAL BOARD
`_____________
`
`MICRO MOTION, INC.
`Petitioner
`v.
`
`INVENSYS SYSTEMS, INC.
`Patent Owner
`
`Patent No. 7,571,062
`Issue Date: August 4, 2009
`Title: DIGITAL FLOWMETER
`_______________
`
`Inter Partes Review No. Unassigned
`____________________________________________________________
`
`DECLARATION OF DR. MICHAEL D. SIDMAN
`
`4812-2280-4248.1
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`1
`
`Micro Motion 1002
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`
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`1.
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`I, Dr. Michael D. Sidman, resident at 6120 Wilson Road Colorado
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`Springs, CO, hereby declare as follows:
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`2.
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`I have been retained by Foley & Lardner LLP to provide my opinion
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`concerning the validity of U.S. Pat. No. 7,571,062. I am being compensated for my
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`time at the rate of $450/hour in preparing this declaration.
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`I.
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`QUALIFICATIONS
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`3.
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`I completed my undergraduate studies at Northeastern University,
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`where I received a Bachelor’s and a Master’s degree in Electrical Engineering
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`concurrently in 1975.
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`4.
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`I received my Ph.D. from Stanford University in 1986. My work at
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`Stanford as a Digital Equipment Corporation Fellow and University Resident
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`included developing a high-performance digital control system for a lightly-
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`damped mechanism in the Stanford Aero/Astro Robotics Laboratory.
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`5.
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`My dissertation was entitled: Adaptive Control of a Flexible Structure.
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`This research culminated in an adaptive control system that actively damps the
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`vibrations of a lightly-damped mechanism, like a large space structure or disk drive
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`actuator, whose resonant frequencies may be unpredictable or variable. The system
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`performed on-line system identification of the frequencies of the mechanism’s
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`mechanical resonances.
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`4812-2280-4248.1
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`6.
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`I have worked for over 35 years in the field of motor, motion and
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`servo control systems, and specifically in the field of digital control and signal
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`processing systems. I have researched the control and mechanical dynamics of
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`high performance, precision digital servo systems such as found in a range of
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`computer peripheral devices.
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`7.
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`Since 1992, I have been working as an independent engineering
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`consultant. I am currently President of Sidman Engineering, Inc. I provide
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`engineering design services to manufacturers worldwide, which span a range of
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`industries. This work has included the following: (1) optimizing and simulating
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`mechatronic systems (2) developing comprehensive custom design and dynamic
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`system simulation tools including computer models of motor, motion and servo
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`control systems; (3) teaching on-site technical short courses to design engineers
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`and scientists; and (4) consulting on high-performance digital servo systems design
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`and problem resolution.
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`8.
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`The field of “mechatronics” encompasses mechanics, electronics and
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`control systems technologies.
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`9.
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`A “servo” or “servomechanical” system is a control system that
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`controls position, velocity or acceleration, often utilizing motion sensor feedback .
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`10.
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`Through Sidman Engineering, I provide interdisciplinary analysis and
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`resolution of complex design issues. This may include providing clients with
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`4812-2280-4248.1
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`customized, comprehensive computer based design tools and simulation models of
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`a variety of dynamic systems, including electromechanical products and systems.
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`These comprehensive models integrate actuator dynamics and electrodynamics,
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`mechanical resonances, electronic circuitry, sensors, signal processing and
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`filtering. In this role I have developed comprehensive servo system simulation
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`models and design tools. The design tools I provide generally are used by product
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`or system design engineers to understand system behavior and to optimize system
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`parameters. As discussed below, I also provide on-site high level technical training
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`courses for design engineers and scientists at companies. My business address is at
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`6120 Wilson Road, Colorado Springs, Colorado, 80919.
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`11. My commercial clients span the following industries and applications:
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` Industrial and commercial: chemical process control, steel
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`manufacturing, hydraulic control, commercial aviation, medical
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`equipment, textile manufacturing, food processing, bicycle motor
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`control, fuel cells.
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` Computer peripherals and related test equipment: hard disk drives,
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`optical disc drives, tape drives, printers, digital pens, robotics.
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` Automotive: tire manufacturing & test, engine and vehicle
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`dynamometers, electromechanical EGR valves, electric power assisted
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`steering.
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`4812-2280-4248.1
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` Chip design: motor, motion and digital servo control IC’s, DSPs and
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`microcontrollers.
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` Defense: aerospace, naval, optical reconnaissance, security scanning.
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` Instrumentation: software, flow meters, optical position sensing,
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`coordinate measurement machines.
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` Telecommunications: digital signal processing, speech analysis,
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`optical switching.
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`This list is simply representative of my technical consulting activities to
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`companies over a period of more than two decades.
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`12. Before I became an independent engineering consultant, I spent 17
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`years at Digital Equipment Corporation (DEC) in roles spanning product
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`development, advanced development and research. I headed DEC’s Advanced
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`Servo Development Group and Servo-Mechanical Advanced Development Group,
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`both of which I founded. These groups developed and demonstrated technology
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`involving, for example, position and velocity sensing, MEMS accelerometers,
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`active vibration control, optimal seek control, piezoelectric head positioning
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`actuators and DSP-based digital servo systems for hard disk drives. In a prior
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`product design development role, I was the Project Engineer for DEC’s RK07 disk
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`drive product.
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`4812-2280-4248.1
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`13.
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`I served as DEC’s representative to the Berkeley Sensor and Actuator
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`Center (BSAC), which conducts industry-relevant interdisciplinary research on
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`micro- and nano-scale sensors and moving mechanical elements and actuators
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`constructed using integrated-circuit technology. I also served as DEC’s
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`representative for servo and mechanical technology to the National Storage
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`Industry Consortium (NSIC).
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`14.
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`I also sponsored applied research and/or researchers at Stanford
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`University, U.C. Berkeley and the University of Colorado at Colorado Springs.
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`15.
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`I have taught numerous courses and seminars relating to the field of
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`mechatronics to product and system design engineers and a graduate level course
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`in Optimal Control at the University of Colorado in Colorado Springs.
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`16.
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`Through Sidman Engineering, I have provided my on-site, customized
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`Digital Servo System Short Courses and MATLAB/SIMULINK/Toolbox
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`Laboratory Training Courses to product development and research engineers and
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`scientists worldwide in a wide range of industries and government entities since
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`1993. These courses may optionally include portions devoted to control systems
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`and/or signal processing analysis and simulation. I developed these courses to
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`enable attendees, who usually represent a range of technical disciplines, to model
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`and simulate dynamic systems and the operation of products they are developing.
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`4812-2280-4248.1
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`17.
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`I became a Third Party Provider for The MathWorks, Inc. in 1993 and
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`authored an invited feature article, entitled “Control Design Made Faster and More
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`Effective,” for MATLAB News and Notes, Summer/Fall 1994.
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`18.
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`I am a member of professional organizations dedicated to control
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`systems and mechatronic technology. I am a Senior Member of the Institute of
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`Electrical and Electronics Engineers (IEEE) where I am a member of the Control
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`Systems Society.
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`19.
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`I am also a member of the American Society of Mechanical Engineers
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`(ASME), where I was Chairman of the Pikes Peak Section and member of the
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`Dynamic Systems and Control Division (DSCD).
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`20.
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`I am the named inventor of eighteen U.S. patents relating to
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`technologies including: analog and digital electronics, digital signal processing,
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`high performance digital servo systems, adaptive runout control, active damping of
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`mechanical vibrations, adaptive control system gain regulation, etc.
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`21.
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`I have published numerous articles relating to control systems, and
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`specifically, articles relating to the motion sensing and control of precision
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`actuators.
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`4812-2280-4248.1
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`7
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`
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`II.
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`INTRODUCTION TO CORIOLIS FLOWMETERS
`
`A. Uses of Coriolis Flowmeters
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`22. Gaspard-Gustave de Coriolis was a French mathematician,
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`mechanical engineer and scientist who lived from 1792 to 1843. Coriolis studied
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`forces as observed from a rotating frame of reference.
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`23. A Coriolis flowmeter is a measurement device used to measure mass
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`flow rate and/or density of a material flowing through an oscillating conduit (i.e.,
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`tube) in the flowmeter. (See, e.g., U.S. Pat. No. 4,872,351, Ex. 1020, 1:49-2:4.)
`
`24. Coriolis flowmeters include one or two conduits through which
`
`material flows. One conduit is described for simplicity, but the discussions herein
`
`are generally applicable to a system with two conduits. (See, e.g., U.S. Pat. No.
`
`4,823,614, Ex. 1021, 1:44-47, 2:51-55.)
`
`25. Coriolis flowmeters measure mass flow rate by sensing the effect of
`
`Coriolis forces on the material flowing through the vibrating conduit.
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`26.
`
`The material flowing in the tube may be a single type of material
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`(single phase) or multiple types of material mixed together (multi-phase).
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`Examples of materials include a wide variety from gas to liquid to near-solid. (E.g.,
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`U.S. Pat. No. 4,679,947, Ex. 1007, 1:41-43 (“two-phase flow”); U.S. Pat. No.
`
`4,823,614, Ex. 1021, 3:14-17 (“highly viscous fluids and thick slurries, for
`
`example, asphalt, latex paint and peanut butter”); U.S. Pat. No. 4,872,351, Ex.
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`4812-2280-4248.1
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`8
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`
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`1020, 1:29-44 (sweetening agent, oil); U.S. Pat. No. 5,068,116, Ex. 1028, 1:18-20
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`(water, syrup for beverage mixing); U.S. Pat. No. 5,143,257, Ex. 1022, 1:7
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`(“medication and/or nutrients”); U.S. Pat. No. 5,148,945, Ex. 1023, 1:12-14
`
`(“ultra-high purity chemicals . . . such as in the manufacture of semiconductor
`
`wafers”).) Examples of multi-phase materials include a gas/liquid mixture, a
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`liquid/solid mixture, and a gas/liquid/solid mixture. (E.g., U.S. Pat. No. 5,224,372,
`
`Ex. 1024, 1:34-38 (“multiphase fluid emanating from oil and gas wells wherein
`
`essentially, mixtures of water, hydrocarbon liquids, such as crude oil; and gas are
`
`continually produced in varying proportions of the total fluid flowstream”); U.S.
`
`Pat. No. 5,317,928, Ex. 1025, 1:17-20; 1:25-30 (“Typically a two-component fluid
`
`mixture consists of either a solid component fully or partially dissolved within a
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`liquid carrier fluid, or a liquid component mixed with a liquid carrier fluid” such as
`
`“sugar in water” in the “beverage industry,” “concentration of TiO2” in the “pulp
`
`and paper industry”).)
`
`27. As described below, Coriolis flowmeters rely on the principle that the
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`mass flow rate of material passing through a sinusoidally oscillating conduit can be
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`determined by sensing conduit twist induced by the Coriolis force. And, the natural
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`frequency of conduit oscillation provides the basis for measurement of the density
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`of the material inside the conduit. The Coriolis flowmeter’s electronics are
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`responsible for initiating, sustaining and, in general, controlling the sinusoidal
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`4812-2280-4248.1
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`9
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`
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`oscillation of the conduit(s). For example, through the use of the conduit motion
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`sensors and an electromagnetic conduit driver or actuator, Coriolis flowmeter
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`electronics provides the mechanical energy to vibrate the conduit and to regulate
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`the amplitude of conduit oscillation. Coriolis flowmeters rely on the persistence of
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`sustained sinusoidal oscillation of the conduits.
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`28.
`
`The flowmeter induces a Coriolis force on flowing material in the
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`conduit by oscillating the conduit, and determines a property of the material based
`
`on information about the effect of the Coriolis force. (See, e.g., U.S. Pat. No.
`
`4,733,569, Ex. 1026, 1:27-36; U.S. Pat. No. 4,823,614, Ex. 1021, 1:47-61.).) For
`
`example, by measuring a phase difference in the sinusoidal oscillation of the
`
`conduit between two points on the tube, it is possible to determine the mass flow
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`rate of the fluid flowing through the tube. Coriolis flowmeters were first
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`commercialized by petitioner Micro Motion in the late 1970s and early 1980s. See
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`U.S. Pat. No. 5,373,745, Ex. 1003, 1:24-25 (“[Coriolis flowmeters were] first made
`
`commercially successful by Micro Motion, Inc. of Boulder, Colorado.”)
`
`B. Components of Coriolis Flowmeters
`
`29. Coriolis flowmeters include the following basic components: a
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`vibratable conduit (which can have various shapes and sizes) through which fluid
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`flows; an electromechanical drive mechanism (including one or more
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`electromagnetic drivers or actuators) for vibrating the conduit; one or more sensors
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`4812-2280-4248.1
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`
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`that transduce the vibration of the tube; and electronics for controlling the drive
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`mechanism and for analyzing signals from the sensors.
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`30. Coriolis (and other) flowmeters were originally implemented with
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`analog electronic components. E.g., U.S. Pat. No. 2,865,201, Ex. 1004. To do the
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`necessary signal processing and control, such an analog flowmeter uses analog
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`components to process signals from the sensors and to control the drive
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`mechanism. As digital electronic components became more readily available,
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`flowmeters also incorporated digital components. (See, e.g., U.S. Pat. No. Re.
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`31,450, Ex. 1005, which discloses a predominantly analog system incorporating
`
`some digital components.) Digital components include digital logic and
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`programmable digital devices (e.g., microprocessors). (E.g., U.S. Pat. No.
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`4,934,196 (“Romano”), Ex. 1006, Fig. 3; U.S. Patent No. 5,009,109 (“Kalotay”),
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`Ex. 1008, Fig. 4; U.S. Pat. No. 5,050,439 (“Thompson”), Ex. 1027, 16:11-15.) A
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`digital flowmeter may include analog and digital components. For example, a
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`digital flowmeter may process signals from the sensors using digital components
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`but control the drive signal using analog components. A digital flowmeter may
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`alternatively control the drive signal using digital components.
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`31.
`
`The flowmeter must process the sensor signals to extract information
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`of interest from other information in the signals. Thus, all flowmeters, whether
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`analog or digital, perform signal processing on the sensor signals. For example, in
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`
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`a Coriolis flowmeter, fluid flowing through an oscillating flowtube may cause a
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`phase shift in the flowtube oscillation due to the Coriolis effect, and the flowmeter
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`processes the sensor signals to extract the information related to the Coriolis effect
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`from other information in the signals to determine mass flow rate or density. If the
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`signal processing is performed in digital components, then the signal processing is
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`digital signal processing.
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`C. Operating Principles
`
`32.
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`The Coriolis effect caused by oscillating a conduit in which fluid is
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`flowing results in a twist in the conduit, with a resulting phase shift in the
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`oscillation between two points physically spaced apart on the conduit. The phase
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`shift is proportional to the mass flow rate of the material.
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`33. A tutorial showing the principles underlying the operation of Coriolis
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`flowmeters may be found at
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`www3.emersonprocess.com/micromotion/tutor/28_flowoprinccurvtubevib.html.
`
`34.
`
`The Coriolis effect as related to a Coriolis flowmeter was described in
`
`a 1990 article by the petitioner, where the term “flow tube” is synonymous with the
`
`term “conduit”:
`
`The Micro Motion flowmeter measures fluid mass in motion. A
`flowmeter is comprised of a sensor and a signal processing
`transmitter. Each sensor consists of one or two flow tubes enclosed in
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`
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`a sensor housing. The principle of operation is the same for all Micro
`Motion sensors.
`The sensor operates by application of Newton's Second Law of
`Motion: Force = mass x acceleration (F = ma). The flowmeter uses
`this law to determine the precise amount of mass flowing through the
`sensor tubes.
`Inside the sensor housing, the flow tube is vibrated at its natural
`frequency (Figure 1) by an electromagnetic drive coil located at the
`center of the bend in the tube. The vibration is similar to that of a
`tuning fork, covering less than a tenth of an inch and completing a full
`cycle about 80 times each second.
`As the fluid flows into the sensor tube, it is forced to take on the
`vertical momentum of the vibrating tube. When the tube is moving
`upward during half of its vibration cycle (Figure 2), the fluid flowing
`into the sensor resists being forced upward by pushing down on the
`tube. Having the tube's upward momentum as it travels around the
`tube bend, the fluid flowing out of the sensor resists having its vertical
`motion decreased by pushing up on the tube (Figure 2). This causes
`the flow tube to twist (Figure 3). When the tube is moving downward
`during the second half of its vibration cycle, it twists in the opposite
`direction. This tube twisting characteristic is called the Coriolis effect.
`Due to Newton's Second Law of Motion, the amount of sensor
`tube twist is directly proportional to the mass flow rate of the fluid
`flowing through the tube. Electromagnetic velocity detectors located
`on each side of the flow tube measure the velocity of the vibrating
`tube. The two velocity signals are sent to the transmitter where they
`are processed and converted to an output signal proportional to the
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`13
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`
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`mass flow rate. Sensor tube twist is proportional to mass flow and is
`determined by measuring the time difference exhibited by the velocity
`detector signals. During zero flow conditions, no tube twist occurs and
`both sides of the tube cross the midpoint simultaneously. With flow, a
`twist occurs along with a resultant time difference between midpoint
`crossing. This time difference appears as a phase shift between the
`two velocity signals and indicates mass flow.
`
`(“How the Micro Motion Mass Flow and Density Sensor Works”, Micro
`
`Motion, Inc., 1990, Ex. 1009, p. 1.)
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`
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`35. Note that in the Micro Motion article, only one conduit (flow tube) is
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`shown. In a one-conduit system, velocity measurements would be made with
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`respect to the housing. In a two-conduit system, velocity measurements are made
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`as relative velocity between the conduits. In either case, the concepts described
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`below apply.
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`36. As seen from the Micro Motion article, measurement of mass flow
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`rate is based on oscillation of the conduit. Similarly, measurement of density is
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`based on frequency of oscillation. Thus, if measurement is being performed,
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`necessarily there will be oscillation.
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`37. Measuring the phase shift described in the Micro Motion article is no
`
`different than measuring phase shift of input signals in any other system, and thus
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`may be addressed by conventional signal processing techniques. Additionally,
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`maintaining oscillation at a desired amplitude and/or frequency is addressed by
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`conventional control theory techniques.
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`D. Control Systems for Coriolis Flowmeters
`
`38.
`
`The control system of the Coriolis flowmeter provides a drive signal
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`to an electromagnetic mechanism (driver) external to the conduit to initiate
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`oscillation of the conduit. The conduit at some point generally settles into
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`sinusoidal oscillation at the resonant frequency (or a harmonic) of the conduit. The
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`resonant frequency of the conduit depends in part on properties of the material in
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`4812-2280-4248.1
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`15
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`
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`the conduit, and may change if the properties of the material change. (See, e.g.,
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`U.S. Pat. No. 4,823,614, Ex. 1021, 2:9-50 3:14-17.) For example, as the density of
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`the material changes (e.g., during aeration, or during transitions from empty to full
`
`and full to empty), the resonant frequency of the flowtube will also change, and the
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`amount of energy required to keep the flowtube oscillating will generally change.
`
`Additionally, because the flowtube is a fixed volume, changes in density will result
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`in changes in mass of the material in the flowtube, and corresponding changes in
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`mass flow rate. The faster the density changes (e.g., in a rapid empty-to-full
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`transition), the more quickly the mass within the flowtube will change.
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`39. As disclosed, for example, in the many prior art patents listed above, a
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`flowmeter incudes a control system that performs at least the following functions.
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`40.
`
`The control system provides signals to the driver to add energy to the
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`oscillation of the conduit as necessary to maintain oscillation of the conduit at a
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`desired frequency (typically at or near the resonant frequency of the conduit).
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`41.
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`The control system receives signals from one or more motion sensor
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`pick-ups mounted externally on the conduit to sense conduit oscillation. These
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`transducers are located apart from each other on the vibrating conduit in order to
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`provide information about conduit torsion induced by the Coriolis forces during
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`flow conditions.
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`
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`42.
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`The control system processes the signals received from the pick-ups,
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`drives the conduits in synchronism with the resonant frequency of oscillation, and
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`determines a property of the material (e.g., mass flow rate and/or density) from the
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`pick-up signals. Information extracted from the pick-up signals (including the
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`property of the material) may be stored, displayed, and/or exported to another
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`system by the flowmeter.
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`43. A block diagram illustration of the relationship between the
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`electronics and conduit of the flowmeter is shown in the figure below by way of an
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`example which uses two pick-ups. The flowmeter electronics includes a drive
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`control system.
`
`44.
`
`The control system of a Coriolis flowmeter therefore performs control
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`functions – processes system input signals and controls system output signals – as
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`described in well-known control theory dating back far before the 1990s (i.e., long
`
`before the filing of the application leading to the patent that is the subject of this
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`
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`Inter Partes Review.) Further, the processing of signals was described by well-
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`known signal processing techniques also dating back far before the 1990s. Some
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`elements of control theory and signal processing techniques will be discussed
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`below.
`
`III.
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`CONTROL SYSTEMS BACKGROUND
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`A. Open Loop Control
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`45. A control system may be used to control the motion of a device or
`
`mechanism. Open loop control refers to a control action without feedback.
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`46.
`
`In a Coriolis flowmeter, open loop control may be used to initially
`
`impart energy into a conduit to initiate oscillation of the conduit. For example, a
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`drive signal having the appropriate spectral content could be used to initially excite
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`resonant vibration of the conduit.
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`47. Because an open loop control system cannot observe actual conduit
`
`motion or the effect of a control action, it cannot, for example, act to regulate or
`
`maintain oscillation amplitude of a conduit. Without feedback, there is no basis for
`
`the control system to modify the drive signal or adjust the control action. Thus,
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`oscillation may decrease, to a stall condition, or oscillation may increase, resulting
`
`in amplifier saturation or even causing damage to the conduit.
`
`B. Closed Loop Control
`
`48. Closed loop control refers to the use of feedback as the basis for
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`control action. For example, a feedback sensor or transducer such as a velocity
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`
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`sensor allows a feedback control system to monitor the effects of its control actions
`
`and to adjust the control action.
`
`49. A servo system is a motion control system. Most servo system are
`
`closed-loop systems which track or follow a desired setpoint or trajectory
`
`command, sometimes referred to as a reference command level or signal. The term
`
`‘servo’ comes from the Latin word servus – meaning servant or slave. A closed
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`loop motion control system may regulate position, velocity or acceleration.
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`50.
`
`The following illustrates a simple example of a closed-loop control
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`system. Closed-loop control relies on feedback (e.g., a feedback loop) to control a
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`“plant” or mechanism in such a way as to make the plant’s output closely track a
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`reference input signal. The “plant” in the figure below is the mechanism whose
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`output is to be controlled. In the case of the Coriolis flowmeter, the plant would
`
`include the conduit driver and the dynamics of the conduit. The pick-ups in a
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`Coriolis flowmeter correspond to the output measuring device in the figure below.
`
`51.In this closed-loop control system, the plant’s output is fed back for comparison
`
`with the reference input, and the difference, or error, is then used as the basis
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`4812-2280-4248.1
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`19
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`
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`for a control or drive signal applied to the plant. The difference (error) is sensed
`
`by the comparator and amplified before being processed by a controller such as
`
`a PI controller, described below. Typically, a power amplifier (not shown)
`
`boosts the drive signal produced by the controller. The blocks illustrated in the
`
`above figure form a control loop that provides a feedback control path which
`
`enables self-correction. The control system produces a dynamically controlled
`
`drive signal by way of a controller or control law that acts to minimize error. In
`
`some control systems, the reference input may be zero. Generally, “a feedback
`
`system has the ability to correct for load disturbances and inaccuracies in
`
`the controller.” (Introduction to Continuous and Digital Control Systems,
`
`Saucedo & Schering, Macmillan, 1968, Ex. 1029, p. 3 (emphasis added).)
`
`i.
`
`Negative Feedback
`
`52.
`
`If the phasing of the feedback acts in such a way as to reduce error,
`
`instead of to accentuate it, then the closed loop control system would be said to be
`
`operating in a stable manner and operating with negative feedback. Stability of
`
`closed loop systems is a key consideration in control systems design. Oscillatory
`
`behavior is an indication that the control system is unstable.
`
`4812-2280-4248.1
`
`20
`
`
`
`ii.
`
`Multi-Loop Feedback
`
`53.
`
`It is common to add an outer control loop to stabilize or enhance the
`
`dynamic performance of an inner control loop (or vice versa). The following is an
`
`example of multi-loop control in a servo system.
`
`(Electromechanical Control Systems and Devices, Canfield, Robert E. Kreiger
`
`Publishing Company, Original Edition 1965, Reprint 1977, Ex. 1030, p. 42.)
`
`54. As described below, an outer control loop can be used to regulate the
`
`amplitude of oscillation of an inner control loop. Prior art patents describing
`
`flowmeters discuss implementing control loops having inner and outer control
`
`loops. (See, e.g., U.S. Pat. No. 4,524,610, Ex. 1031, Fig. 6; U.S. Pat. No. 4,655,089
`
`Ex. 1047, Fig. 9.)
`
`iii.
`
`Positive Feedback
`
`4812-2280-4248.1
`
`21
`
`
`
`55.
`
`If the feedback signal is in phase with the error signal, the closed loop
`
`control loop is said to be operating with positive or regenerative feedback, i.e.,
`
`there is positive loop gain around the feedback loop. “Two alternating quantities
`
`are said to be "in phase" when their maximum values occur at the same instant of
`
`time.” (Dictionary of Mechanical Engineering, Fourth Edition, Nayler,
`
`Butterworth-Heinemann, 1996, Ex. 1013, p. 277.) When positive feedback occurs,
`
`disturbances or oscillations may naturally increase even without, for example, a
`
`reference input. An example of a closed loop system having positive feedback is
`
`the squealing sound produced by speaker to microphone feedback in a public
`
`address system.
`
`IV.
`
`SINUSOIDAL OSCILLATORS
`
`56. While most feedback control systems are designed to avoid positive
`
`feedback, electronic sinusoidal oscillators have long been designed to employ
`
`positive feedback to sustain oscillation. Coriolis flowmeters are, in fact, sinusoidal
`
`oscillators, in which the dynamic elements include the resonant mechanical
`
`dynamics of the conduit.
`
`57. With respect to a sinusoidal oscillation, such as that which is
`
`(desirably) established in a Coriolis flowmeter conduit, a regenerative positive
`
`feedback control loop was used in prior art flow meters to maintain the amplitude
`
`of sinusoidal oscillation of the conduits at a desired value. (See, e.g., U.S. Pat. No.
`
`4812-2280-4248.1
`
`22
`
`
`
`4,524,610, Ex. 1031, 7:45-50 (“a positive feedback circuit is interconnected
`
`between the detector coil 2a and the torsional driver coil la, and the power supplied
`
`to the driver coil la in order to maintain a predetermined amplitude of torsional
`
`oscillation of the tube 50 is measured”); U.S. Pat. No. 4,934,196, Ex. 1006, Fig. 4.)
`
`58. Analog circuit engineers used positive (i.e., regenerative) feedback in
`
`sine wave oscillator designs at least back to the early 1970s to maintain oscillation
`
`amplitude, as described in the following excerpt.
`
`[The following figure] shows an amplifier, a feedback network,
`and an input mixing circuit not yet connected to form a closed
`loop.
`
`The amplifier provides an output signal x0 as a consequence of
`the signal xi applied directly to the amplifier input terminal. The
`output of the feedback network is xf = ßx0 = Aßxi, and the
`output of the mixing circuit (which is now simply an inverter) is
`x’f = -xf = -Aßxi
`From [the figure] the loop gain is
`Loop gain = x’f / xi = -x’f /xi = -ßA
`
`4812-2280-4248.1
`
`23
`
`
`
`(Integrated Electronics: Analog and Digital Circuits and Systems, Jacob Millman
`
`and Christos Halkias, McGraw-Hill, 1972, Ex. 1032, p. 483.)
`
`59.
`
`In the figure above, if points 1 and 2 were connected and the
`
`relationship x’f = xi were true (i.e., the waveforms x’f and xi were identical in
`amplitude, phase and frequency for a sinusoid), then loop gain -ßA would be equal
`
`to one (unity). Unity gain is called the Barkhausen Criterion, which expresses a
`
`necessary, but not sufficient, condition for sine wave oscillation in a positive
`
`feedback control loop. The Barkhausen Criterion is described in the following
`
`excerpt:
`
`The frequency at which a sinusoidal oscillator will operate is
`the frequency for which the total shift introduced, as a signal proceeds
`from the input terminals, through the amplifier and feedback network,
`and back again to the input, is precisely zero (or, of course, an integral
`multiple of 2π.) Stated more simply, the frequency of a sinusoidal
`oscillator is determined by the condition that the loop-gain phase shift
`is zero.
`Oscillations will not be sustained if, at the oscillator frequency,
`the magnitude of the product of the transfer gain of the amplifier and
`the magnitude of the feedback factor of the feedback network (the
`magnitude of the loop gain) are less than unity.
`(Integrated Electronics: Analog and Digital Circuits and Systems, Jacob Millman
`
`and Christos Halkias, McGraw-Hill, 1972, Ex. 1032, p. 484 (emphasis omitted).)
`
`4812-2280-4248.1
`
`24
`
`
`
`60.
`
`The signal x’f can be provided by another source instead of as
`feedback from the output, as long as the Barkhausen Criterion is maintained. Thus,
`
`for example, when the oscillation is relatively stable, knowledge of the oscillation
`
`(such as frequency and phase for a sinusoid) may be used to synthesize a
`
`waveform to be applied as x’f without directly feeding back the signal xo.” since the
`amplifier has no means of distinguishing the source of the input signal” (id.)
`
`Moreover, the concepts described with respect to the figure above may be
`
`implemented in software such that a synthesized drive signal may be provided
`
`directly to the electromechanical device driving the oscillation (i.e., the driver.)
`
`A. Problems Faced by Sinusoidal Oscillators
`The Integrated Electronics 1972 textbook cited above identifies a
`
`61.
`
`number of issues found in sinusoidal oscillators using positive feedback, which are
`
`also key issues found in the control of an oscillating conduit in a Coriolis
`
`flowmeter.
`
`62. An example of the problems described is a problem of oscillation
`
`initiation using regenerative feedback: the oscillator is not guaranteed to start, may
`
`not lock onto the desired frequency of oscillation, or may oscillate at more than
`
`just the desired frequency of oscillation. A number of techniques have been
`
`proposed over the years to “kick start” Coriolis Flowmeter vibration with various
`
`open or closed loop techniques.
`
`4812-2280-4248.1
`
`25
`
`
`
`63. Another example of
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