Compendium of references for electronic motion control
See motion control, motor control article series references, additional motors, drives, and motion control discussion, and 6 more images from the Control Engineering archives.
This is the last online extension (4 of 4) of the main article "Electronic motion control, then and now" appearing in CE's 60th anniversary issue, September 2014. A listing of all references cited in the main article and three related online articles is provided here. Link to all here.
This compendium of references consists largely of articles that have appeared in Control Engineering and its online publications. However, some other sources are also included. A brief abstract is included for each reference. URLs are provided for references dated after 1997; for older references not available online, other reference details are provided. The first four references are the online extensions to the main Sept 2014 article.
1) Electric motors' influence on motion control (online extension 1)
2) Further developments in motion control (online extension 2)
3) Motion control from the archives (online extension 3)
4) Compendium of references (online extension 4) =============================
Probably the most versatile among motor control methods, ac variable-speed drives (VSDs) are available in three principal flavors. Open-loop control, sensorless vector control that eliminates the shaft encoder, and flux vector (field-oriented) control provide increasingly sophisticated command of induction motors and permanent magnet synchronous motors.
Physical size and weight provide the most visible evidence of the remarkable evolution of ac variable-speed drives in the past 50 years. However, what's under the skin is even more dramatic for the performance, efficiency, and reliability now delivered by these controls. Making it all happen were advances in power-switching transistors, microprocessors, other hardware, plus software functions that ease users' concerns for drive application and maintenance. . . And the evolution is accelerating.
Field-oriented control (FOC)-sometimes called flux-vector control-is a method that enables the highest performance from permanent magnet synchronous (or brushless servo) motors throughout their speed range. FOC algorithms model the torque-generating efficiency of dc motors and allow linear torque control. Better known in connection with ac induction motors, for which the technique was first developed, FOC is available for brushless servo motors from many manufacturers. FOC has different flavors and variants, much like vector control of induction motors.
Most high-performance servo systems employ an inner control loop that regulates torque. This inner torque loop will then be enclosed in outer velocity and position loops to attain the desired type of control. While the designs of the outer loops are largely independent of motor type, the design of the torque loop is inherently specific to the motor being controlled.
Comparison of the technologies is provided along with a look at selection guidelines. Tables present motor selection criteria and a comparison of three drive technologies: vector control, brush-type servo, and brushless servo.
10) Direct torque control comes to AC drives, Control Engineering, March 1995, Vol.42, No.3 (p. 9).
Direct torque control (DTC) is made possible by the combination of two factors: high-speed digital signal processing technology and an accurate motor model. The sophisticated motor model is necessary because no shaft speed or position feedback device is required.
Most variable-speed drives in the market rely on a modulator stage that conditions voltage and frequency inputs to the motor, but causes inherent time delay in processing control signals. In contrast, premium ABB drives employ innovative direct torque control (DTC)-greatly increasing motor torque response.
Many products, especially those involving complex motion, require more detailed scrutiny of how well the design will work. This is where simulation software comes into play. Simulation can provide a "virtual prototype" of the product or machine before a physical model is built. Simulation can also cut down on costly physical testing-though not entirely eliminate it.
How to apply simulation software to motion control: Computer simulation software can drastically reduce the cost and time required to design and deploy your next motion-control system, but if you aren't careful, it can lead you down a primrose path to disaster.
MSC Software's Adams and Easy5 Simulation software models and simulates motion control systems to improve machine performance.
Presentation includes an interesting timeline of developments for power semiconductor devices (p. 43).
The number of motion axes found in industrial automation systems has grown steadily over time because of availability of more powerful controllers and processor advancements. Yet, in many of those systems, motion axes function independently of each other. In contrast, more complex automation systems require synchronization of various motion axes. A higher breed of control is required to satisfy multi-axis motion in robotic systems, printing machines, computer numerical control (CNC) machines, and high-dynamic manufacturing lines. Fast network protocols are available to implement the data transfer and control needs.
Inside Machines: Simpler, more advanced, cost-effective motion control techniques hone a competitive advantage in new machine designs for Sunnen, a precision original equipment manufacturer.
AKD Basic and AKD PDMM servo drives from Kollmorgen represent the range of solutions designed from simple single-axis control up to 128 axes of complex and programmable synchronized motion. AKD Basic incorporates a programmable single-axis motion controller into the existing AKD drive footprint and eliminates the need for a separate PLC. AKD PDMM combines a high-performance multi-axis motion controller, complete IEC61131-3 soft PLC, EtherCAT master, and AKD servo drive in one compact package.
High-resolution and encoderless feedback methods, along with software tools, aid the process. More user awareness and cost are needed to expand servo markets.
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