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 an internal fault happens to stop the drive in a controlled way.

Attention: 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.

Note: For detailed Error Report Object with Fault Reaction information, refer to the highlighted (in yellow) information contained in this worksheet.

Usage

Quickstop will be enabled if one of the following conditions occurs:

  • Bit 2 (quick stop bit) of the Controlword changed from 1 to 0 (transitions 7, 10, 11 according to the drive state machine diagram.

  • A drive fault is triggered

  • The drive dropped from EtherCAT Operational state while it was in CiA402 Operational Enabled state

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

During the procedure, torque offset can be used to compensate for possible torque from the load.

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 the 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. After the end of the quick stop ramp, the drive is disabled, which automatically engages the brake as defined by the brake settings.

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 the 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. After the end of the quick stop ramp, the drive continues to stay in Quick Stop Active until a command to disable the drive is received. In position control modes (Cyclic Synchronous Position mode, Profile Position mode, Cogging recording, Homing), Quick Stop Active drive keeps the current position.

    In velocity control modes (Profile velocity mode, Cyclic Synchronous Velocity Mode), the drive controls 0 velocity.

Attention: The brake is not engaged by default in this state.

Torque control mode

In torque modes (Cyclic Synchronous Torque mode, Profile torque mode) the quick stop procedure does not use a profile. 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 immediately disabled.

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

  1. At the moment when quick stop is triggered, torque demand and torque offset are applied according to their values. If the torque profiler is active, the profiler is deactivated. The torque values can be adjusted from the master side.

  2. Concurrently, the timeout period begins. The timeout period is calculated as actual motor velocity divided by the quick stop deceleration. Thus, the user can configure the maximum duration of the quick stop procedure.

  3. During the timeout period, the drive monitors whether the drive reaches zero velocity. When one of the following conditions becomes true, the brake gets engaged and the drive is set to state Switch On Disabled:

    • The actual velocity of the motor reaches 0.

    • The timeout period expires.

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

Option code 6 behaves similarly to option code 2, with the following exceptions:

  • The drive does not transit to state Switch On Disabled, but remains in state Quick Stop Active.

  • Torque demand and torque offset keep being applied.

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

Parameters

Object ID Name Description
0x605A Quick stop option code Select the action that is performed when the quick stop function is executed
0x6085 Quick stop deceleration Defines the quick stop ramp
0x6040 Controlword Shows the drive’s transition into a different state. Use this object to monitor the drive’s behavior
0x60A9 SI unit velocity This object defines the velocity value
0x60FC Position demand internal value Provides the output of the trajectory generator in profile position mode
0x6064 Position actual value Provides the actual value of the position encoder
0x606B Velocity demand value Output of position controller in position mode/trajectory generator in velocity mode
0x606C Velocity actual value Provides the value read at the velocity sensor (or the derivation of the position signal)
0x6074 Torque demand Provides the output value of the torque trajectory generator
0x6077 Torque actual value Provides the actual value of the torque