PLC Servo Motor Control: Three Methods Explained with Examples

PLC Servo Motor Control: Three Methods Explained with Examples

I. Torque Control

In torque control, the motor's output torque is set via an external analog signal or by assigning a value to a specific address. For instance, if 10V corresponds to 5Nm, a 5V signal would set the torque to 2.5Nm. The motor will drive a load smaller than 2.5Nm forward, hold at 2.5Nm, and reverse under loads exceeding 2.5Nm. Torque can be adjusted in real - time by changing the analog signal or updating the address value via communication.

II. Position Control

Position control involves setting the motor's speed with the frequency of external pulses and its position with the number of pulses. Some servos allow direct speed and position value assignment via communication. Due to its precise speed and position regulation, this mode is ideal for positioning systems.

III. Velocity Control

Velocity control can be achieved using analog signals or pulse frequencies. When used with an external PID control loop, velocity control can also enable positioning, provided the motor's position or load position is fed back to the controller for calculations.

SINAMICS V90 System Illustration

The SINAMICS V90 offers two versions to suit different applications:

Pulse Version: Integrated with pulse, analog, USS/MODBUS functions.

PROFINET Version: Designed for PROFINET communication.

The pulse version supports internal positioning block functions, offering modes like pulse position control, velocity control, and torque control.

Interface Definitions

The pulse version uses the PTI interface with default settings that align with standard application practices. Only one pulse input channel can be used at a time, while other control signals can be freely assigned to digital I/O terminals. The 24V power supply shown in the wiring diagram is for the SINAMICS V90. All PTO signals must connect to a controller using the same 24V power source. The digital inputs support both NPN and PNP types.

Brake Cable Connection for SINAMICS V90

The brake cable connection shown applies only to the V90 400V drive. The V90 200V drive requires an external relay for motor brake connection.

System Wiring Diagrams

For the V90 200V drive, an external relay is needed for motor brake connection.

The PTI drive connects to a relay via a setpoint cable, while the PROFINET drive uses an I/O cable.

For PROFINET 200V drive brake control and applications requiring additional DI/DO beyond PROFINET communication, an I/O cable must be used.

Motor Connections

SIMOTICS S - 1FL6 low - inertia motors (SH20, SH30, SH40) use cable - type connectors.

The brake cable connection shown is only for the V90 400V drive.