Michael K. Masten

Digital signal processors for modern control systems

Abstract The development of improved “control theories” has been an on-going activity, and several truly outstanding control methodologies have been developed. Meanwhile, modern integrated circuit technology has produced the Digital Signal Processor (DSP), which offers substantial computational power at readily affordable prices. These parallel developments offer an unprecedented opportunity for practical implementation of advanced control techniques. As a result, sophisticated control-system applications using DSPs have increased exponentially in recent years. This paper provides an overview of DSPs, reviews their key features, outlines procedures for using DSPs, and reviews some of todays major DSP control-system applications.

Electromechanical System Configurations For Pointing, Tracking, And Stabilization Applications

A line-of-sight (LOS) stabilized platform is an electromechanical subsystem designed to isolate a payload from its environment and point the load in a given direction as it operates in its environment. There are numerous mechanical configurations which may be chosen for design of the stabilization system. Mass Stabilization refers to the class of designs in which the entire payload is supported by a gimbal assembly with as low as practical friction in the gimbal bearings; this approach exploits the inherent tendency for a mass to retain its orientation in inertial space. The control loop is then designed to attenuate the effect of inadvertent torque disturbances due to friction, unbalance and/or other disruptions. Mirror Stabilization refers to the class of designs in which a mirror (or optical element which can alter the LOS) is controlled to achieve steady LOS orientation. The mirror arrangement has an inherent two-to-one optical doubling effect which must be accounted for in the design. Other mechanical configurations also are possible; indeed practical designs may use a combination of several. This paper describes the following approaches to the stabilization and tracking tasks: mass stabilization, mirror stabilization, gear-driven gimbals, and momentum wheels. Block diagrams are given for each approach which are then used to discuss the advantages and limitations of each.

Electronics: The intelligence in intelligent control

Abstract The control systems field has a rich legacy of continuous improvement in control “techniques”. Today we are developing powerful “intelligent control” methods which incorporate adaptation, learning, self diagnosis (and reconfiguration/repair), as well as other attributes which promise dramatic performance beyond all our prior accomplishments. At the same time that dramatic advancements have occurred in control “methodologies”, there has been a parallel evolution in control hardware. Smaller, lower power sensors provide more accurate information regarding system operation, actuators provide more efficient, higher precision control inputs, and controller hardware now performs much more complex algorithms. More powerful electronics, developed over the last two decades, have made these hardware advancements possible. Microprocessor and Digital Signal Processor technology has been a key contributor to these advancements. By incorporating these electronics, today’s control engineers may use “Smart Sensors”, “Smart Actuators”, and “Intelligent Controllers” in their control system designs. Furthermore, plans within the electronics field guarantee that future control systems can be fabricated with even greater capabilities.

Switched reluctance motor control techniques

This paper provides a basic tutorial on SRMs, how they are controlled, and potential applications. A review of the equations governing the operation of the SRM is given and the operation of the SRM is described. Current control, commutation algorithms, and techniques for reducing torque ripple and linearizing the SRM torque response are discussed. Algorithms which allow motor operation without aid of a shaft position sensor are introduced.

An Industrial Challenge to Control System Educators

Abstract Most engineers earn their livelihood in industry. Technological advancements and industry trends guarantee that these engineers will face significant challenges during their career. Meanwhile, advancements in control theory insure that many diverse control techniques will be used. This paper identifies seven challenges for educators who are preparing tomorrow’s control system engineers.

A strategy for industry's continuing education needs

Abstract Todays engineers face the difficult task of maintaining vitality during a time of rapid technological change. With worldwide competition and massive industrial “right-sizing”, traditional mentoring and informal training is no longer sufficient to enable young engineers to achieve the levels of competence expected for such professionals. Experienced engineers likewise face similar challenges as technology moves beyond the levels that were current at the time of their formal education. In early 1993, the Education Activities Board of the IEEE approved plans for INDUSTRY 2000, a workshop designed to bring together leaders from industry, technology experts, and continuing education providers, to (1) identify industrys continuing education needs and (2) to define a strategy through which IEEE, industry, and academia can work together to maintain technical vitality of engineering professionals. This paper reports on the results of INDUSTRY 2000, particularly as they apply to Continuing Education within Control Systems technology.

Digital signal processor: a control element

Practical control systems increasingly use DSPs. DSPs have specialized high speed architectures and tailored instruction sets which execute in a single machine cycle; in addition, the hardware multiplier handles single instruction cycle multiply/add (accumulate) operations. DSPs are therefore geared for high-speed digital signal processing which is a basic operation in modern control algorithms. This paper overviews DSPs, reviews key features, and outlines processes for using DSPs in control applications.

Adaptive Friction Compensation for Line-of-Sight Pointing and Stabilization

This paper presents a new and practical adaptive friction compensation (AFC) technique developed at Texas Instruments for either analog or digital implementation. AFC is designed to augment conventional stabilization rate loops for the purpose of adapting to the characteristics of friction and canceling its torque disturbances before they cause LOS jitter. Estimates of coulomb friction level (CFL) and spatial time constant (STC), a measure of the disturbance rise time, are generated in real-time using a novel algorithm with minimal computational requirements. These estimates of CFL and STC are used to update a simple friction reference model which generates commands to cancel friction disturbances using relative rate feedforward. Laboratory tests show that stabilization can be improved by 90% to 75% depending on the base rotary environment characteristics: a) single sinusoid and b) band-limited random, respectively.

Introduction to a Showcase of Adaptive Controller Designs

The Adaptive Control literature contains hundreds of technical papers on many different approaches to the subject. However, engineers who are not specialists in adaptive theory often have difficulty selecting which approach to use in any given problem. This invited session addresses this situation by defining a set of standard problems which are then solved by several of todays distinct approaches to adaptive control. This introductory paper explains the motivation for this session and then defines the problems and guidelines which will be followed in subsequent presentations.

Applications of Control Theory to Design of Line-of-Sight Stabilization Systems

Line-of-sight stabilization systems control the inertial orientation of critical payloads. Requirements for these systems have steadily increased due to improved resolution of payloads, higher maneuverability of host vehicles, and increased overal precision necessary to accomplish mission objectives. The conventional design approach is to develop a stabilization subsystem to minimize inertial jitter and then design a track subsystem to control the overall orientation. Achieving these goals is dependent upon the capability to reject environmental and application induced disturbances.