Quick stop

Overview

When the drive is in motion and the user wishes to stop quickly for any reason, the Quick Stop state can be activated. This function uses a profile to drive the motor from the current velocity down to zero with a specific Quick Stop deceleration. Quick stop can also be performed when a fault happens to stop the drive in a controlled way.

Attention

Note that the brake might get damaged when the motor does not ramp down to zero velocity. This can happen due to one of the following reasons:

  • when the motor is mechanically unstable

  • when the control system is unstably or poorly tuned

  • when the quick-stop feature is misconfigured

If no brake exists, this can even lead to a damaged motor!

Note

At the end of the quick stop procedure the brake gets engaged when the drive is in SWITCH_ON_DISABLED (mode 2). When the drive stays in QUICK_STOP_ACTIVE (mode 6) the brake is not engaged by default.

Usage

Quickstop will be enabled if Bit 2 in control word changed from 1 to 0 if the actual control state is 7, 10 or 11.

Object 0x605A Quick stop option code has different options that switch the drive into different states:

Option code

Definition

0

Disable drive function (no quick stop deceleration)

2 (default)

Slow down on quick stop ramp and transit into switch on disabled

6

Slow down on quick stop ramp and stay in quick stop active

The execution of the procedure depends on the operational mode that is active:

Position and velocity control modes

The steps vary depending on the quick stop option code and when quick stop is triggered:

Option code: 0 (Disable the drive)

Attention

In this case, the drive does not perform the quick stop deceleration ramp and is instead immediately disabled.

Option code: 2 (Slow down on quick stop ramp and transit into switch on disabled)

  1. The Drive commands a quick stop ramp that ramps down an effective commanded velocity according to user defined quick stop deceleration.

  2. The end of the quick stop ramp is a moment when the commanded velocity is equal to 0.

  3. A timeout period of 100 ms is started in which the drive commands a fixed position or zero velocity.

  4. During that period the drive observes if the actual velocity of motor has reached 0.

  5. If one of the following conditions are met, the drive is disabled which automatically engages the brake as configured:

    • The actual velocity of the motor has crossed or equals zero.

    • The timeout period has expired

Option code: 6 (Slow down on quick stop ramp and stay in quick stop active)

  1. The Drive commands a quick stop ramp that ramps down an effective commanded velocity according to user defined quick stop deceleration.

  2. The end of the quick stop ramp is a moment when the commanded velocity is equal to 0.

  3. A timeout period of 100 ms is started in which the drive commands a fixed position or zero velocity.

  4. During that period the drive observes if the actual velocity of motor has reached 0

Note

The drive continues to stay in Quick Stop Active until a command to disable the drive is received.

Attention

In this state the brake is not engaged by default.

Torque control mode

In torque modes (Cyclic Synchronous Torque mode, Profile torque mode) the quick stop procedure does not use a profile. Instead, the drive commands 0 torque from the start of the quick stop procedure. The steps vary depending on the quick stop option code and when quick stop is triggered:

Option code: 0 (Disable the drive)

Note

In this case, the drive does not perform the quick stop deceleration ramp and is instead immediately disabled.

Option code: 2 (Slow down on quick stop ramp and transit into switch on disabled)

  1. The Drive commands zero torque

  2. At the same moment the timeout period is started which lasts for 1000 ms

  3. The brake gets engaged and the drive is set to state Switch On Disabled, if one of the conditions are true:

    • The actual velocity of the motor reached 0

    • The timeout period has expired

Option code: 6 (Slow down on quick stop ramp and stay in quick stop active)

  1. The Drive commands zero torque

Note

The drive continues to stay in Quick Stop Active until a command to disable the drive is received. Transition 16 from Quick Stop Active to Operation Enabled is not supported.

Note

When quick stop is commanded during Offset detection, the procedure is aborted and the drive is disabled.