Trapezoid Motion

Provides the velocity commands to the motor drive that will achieve the fastest trapezoidal move from the current position to the Position Setpoint.

It is important to set the ramp times to realistic values. The motor must be able to accelerate or decelerate to 100% speed within that time. Do not set to a value less than the built-in ramp times in the drive.

The exact setting of the Nominal Time parameter is critical and must be carefully calculated. A convenient calculator is provided by clicking on the 'i' information button that is displayed in that parameter's box in the function block view. The nominal time is the exact number of seconds that it takes for the position error to change by 100% at a continuous 100% speed. Generally, when the nominal time is set too short, the target will be undershot. With the time too long, the target is overshot.

Click on the Tuning button to view or change more details regarding the loop latency and final approach.

Latency should represent the realistic complete loop latency including mechanical, motor, drive, comms, update times, etc. Extending the latency is required with slower loops to avoid overshoot.

Set Final Approach at zero at first because there is typically enough momentum during the latency period to complete the move.

• Available only in the dw2xx & dw2xx-v2 series products
• Requires library: Motion Control (option -36) or Precision Motion (option -39)
• Firmware versions 0x201C through 0x2105

Trapezoid Motion - Position Setpoint

The position demand input.

Speed Setpoint will be zero when Position Feedback = Position Setpoint.

Trapezoid Motion - Position Feedback

The current position.

Speed Setpoint will be zero when Position Feedback = Position Setpoint.

Trapezoid Motion - Speed Setpoint

The output of the Trapezoid Motion function block.

The velocity demands that will achieve the fastest move from the current position, Position Feedback, to move to the target postion, Position Setpoint.

Trapezoid Motion - Status

The current state of the move.

Equals zero for 'Move Complete' and non-zero when moving. This can be useful (convenient) for machine-sequencing.

Trapezoid Motion - Max Speed

This speed may not be reached with long ramps and / or short moves.

Status indicates Speed Clamped when this speed is reached.

Trapezoid Motion - Acceleration Time

The time to accelerate from zero speed to Maximum Speed.

This time is usually be determined by the capabilities and requirements of the application. Factors may include available motor torque, gain requirements and load momentum.

Trapezoid Motion - Deceleration Time

The time to decelerate from Maximum Speed to zero speed.

This time is usually be determined by the capabilities and requirements of the application. Factors may include available motor torque, gain requirements and load momentum.

Trapezoid Motion - Tuning - Latency

The time in ms required for the position loop to update completely.

It is important to set this correctly to avoid overshoots and instability.

Consider all elements in the position loop that may contribute to latency; position feedback, velocity demand output, motor-drive velocity and torque loop propagation delays, mechanical latency.

Trapezoid Motion - Tuning - Final Approach

Controls the position-control gain near the target position.

Higher values are more responsive and will approach more quickly. Excessive values may cause instability (small oscillations around the target position).

Trapezoid Motion - Hold

Hold causes Speed Setpoint to immediately reset to 0.00% when activated.

Speed Setpoint accelerates according to Acceleration Time after Hold becomes Inactive.

Trapezoid Motion - Pause

Pause causes Speed Setpoint to ramp to 0.00% according to Deceleration Time when active.

Speed Setpoint accelerates according to Acceleration Time after Pause becomes Inactive.