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SynqNet Demand Modes

Introduction

SynqNet supports Torque and Velocity demand modes. The demand mode determines the size and type of control signal between the controller and the drive. In the future, SynqNet will also support Position demand mode. The demand mode is configurable when the amplifier is disabled. On-the-fly switching requires some special techniques to smoothly transition between demand modes.

During SynqNet network initialization, the nodes are discovered and the demand mode is automatically set to a default, based on the particular drive model. The number of 16-bit demand fields (1, 2, or 3) per motor are configured and connected to the controller’s filter (closed-loop servo algorithm). The default is the recommended mode, but the user can change the demand mode using mpiMotorConfigGet /Set(...) in the MPIMotorConfig.demandMode value (found in the external structure in mpiMotorConfigGet /Set(...).

Not all demand modes are supported by each node or drive. RMBs and analog drives will only support ANALOG and those with two DACs per axis will only support ANALOG_DUAL_DAC. Drives that support a drive processor interface will support TORQUE and those that have velocity loops will also support VELOCITY (Kollmorgen S300, S600, and S1800).

Torque Mode

In Torque Mode, the output of the closed-loop servo algorithm (PID or PIV) is a 16-bit value representing torque. See the servo algorithm diagrams on Servo Algorithms PID/PIV. This 16-bit demand value is sent cyclically to the drive in the DEMAND packet via the demandA field. See DEMAND Packet for more details.

For RMBs, the ANALOG mode is a variation of Torque mode. The only difference is that the 16-bit demand value is sent via the dac0 field. The ANALOG_DUAL_DAC mode provides an additional dac1 field. ANALOG_DUAL_DAC is useful for applications that need a second DAC for auxiliary purposes or if two DACs are needed for sinusoidal commutation.

Velocity Mode

In Velocity Mode, the output of the closed-loop servo algorithm (PID or PIV) is a 16 bit value representing velocity. See the servo algorithm diagrams on Servo Algorithms PID/PIV. This 16-bit demand value is sent cyclically to the drive in the DEMAND packet via the demandB field. See DEMAND Packet for more details.

For drives that support Velocity Mode, the drive automatically scales its velocity demand input so that the 16-bit range is used effectively.

The demandA field is used to send Acceleration Feed-Forward, Friction Feed-Forward, and Offset via the torque demand to the drive.

Velocity mode is not applicable to RMBs.

See Also:

MPIMotorDemandMode

 

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