NP5 CANopen Online Manual

Automatic brake control

Description

Automatic brake control is activated if the controller is switched to the Operation enabled state of the CiA 402 Power State Machine; the brake otherwise always remains closed.

The brake output of the controller results in a PWM signal that can be adjusted with respect to frequency and duty cycle.

For information on the interaction of the brake with the motor stopping behavior, see also chapter Power State machine – halt motion reactions.

Activation and connection

The brake can be controlled either automatically or manually:

  • Automatic: Setting bit 2 of object 3202h to "1" activates the brake control.
  • Manual: Setting bit 2 of object 3202h to "0" deactivates the brake control; the brake can now be controlled with bit 0 in object 60FEh.

Brake control

The following graphic shows the states of the CiA 402 Power State Machine together with the states of the brake for the automatic mode.

The following steps are performed on the transition, which is marked with 1:
  1. The motor current is switched on.
  2. The time stored in 2038h:3h is allowed to elapse.
  3. The brake releases.
  4. The time stored in 2038h:4h is allowed to elapse.
  5. The Operation enabled state is reached, the motor controller can perform travel commands.
The following steps are performed on all transitions that are marked with 2:
  1. The motor is brought to a standstill.
  2. The time stored in 2038h:1h is allowed to elapse.
  3. The brake is activated.
  4. The time stored in 2038h:2h is allowed to elapse.
  5. The motor current is switched off.

Brake PWM

The switched-on brake generates a PWM signal at the output of the controller that can be adjusted with respect to duty cycle and frequency. If an output pin without PWM is needed, a duty cycle of 100 percent can be set.

Frequency

The frequency of the brake PWM can be set in object 2038h:5h. The unit is Hertz; a value greater than 2000 is not possible.

Note: If the PWM signal of the brake causes interfering noise, it can be eliminated by connecting a 47 µF … 100 µF capacitor in parallel at the brake output.

Duty cycle

The duty cycle – the ratio of pulse to period duration – is set in 2038h:6h. The value is a percentage and can be selected between 1 and 100. With a value of 100, the output pin is permanently switched on.

In the following figure, example duty cycles of 25 and 50 percent are shown, whereby the frequency is held constant.

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