Motion Control Methods
Within this basic motion control paradigm, there is latitude for different control methods, both closed loop and open loop. By closed loop, it is implied that there is a feedback signal that is used to drive the actual dynamics of the motor to match the commanded dynamics by the servo action.
In most cases, there is a literal feedback device to provide this signal, and in some cases the signal is derived from the motor excitation, for example, sensorless/encoderless operation.
By open loop, it is implied that there is no application of feedback to force the actual dynamics to match the commanded dynamics. While precision and performance are the hallmarks of closed loop control, simplicity and economy are the hallmarks of open loop control.
The Control Method attribute is an 8-bit enumerated code that determines the basic control algorithm. The device applies the algorithm to control the dynamic behavior of the motor that is associated with an axis. The Control Methods related to the Control Modes are listed in the following table.
Control Method Filed Enumeration Definitions
Enumeration | Usage | Name | Description |
|---|---|---|---|
0 | R/N | No Control | No Control is associated with a Control Mode of No Control where there is no explicit motor control that is provided by the device for this axis instance. |
1 | R/F | Frequency Control | Frequency Control is an "open loop" control method that applies voltage to the motor, generally in proportion to the commanded frequency or speed. This control method is associated with Variable Frequency Drives (VFDs) or so called Volts/Hertz drives. |
2 | R/C | PI Vector Control | PI Vector Control is a "closed loop" control method that uses actual or estimated feedback for closed loop cascaded PI control of motor dynamics, that is, position, velocity, acceleration, and torque, and always includes independent closed loop PI control of Iq and Id components of the motor current vector. |
3...127 | - | Reserved | - |
128...255 | - | Vendor Specific | - |
Axis configuration
The Control Mode and Control Method are derived by the Axis Configuration according to the following table.
Axis Configuration | Valid Control Modes |
|---|---|
Non-Regenerative AC/DC Converter | No Control |
Regenerative AC/DC Converter | No Control |
Low Harmonic AC/DC Converter | No Control |
DC/DC Converter | No Control |
Feedback Only | No Control |
Frequency Control | Velocity Control |
Position Loop | Position Control Velocity Control Torque Control |
Velocity Loop | Velocity Control Torque Control |
Torque Loop | Torque Control |
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