MIR 250 Hook - Safety Stop

11. Safety-related functions and interfaces
MiR250 Hook User Guide (en) 01/2023 - v.1.2 ©Copyright 2021-2023: Mobile Industrial Robots A/S. 130
The interfaces are used to communicate with the hook and connect to the Emergency stop
button.
Component monitoring
The hook computer monitors the components within the hook to ensure they are operating
correctly and the hook does not pose a risk to nearby personnel. If the hook computer detects
any discrepancies or errors from the hook components, it relays this information to the robot
computer via the Ethernet connection, and the robot enters Protective stop if the error indicates
that the hook cannot be controlled reliably.
11.7 Safety stop
There are two pairs of contactors used to stop MiR250 Hook: the STO (Safe Torque Off) contactors
and the SS1 (Safe Stop 1) contactors. These are controlled by the safety PLC and are used when
the robot goes into Protective or Emergency stop. The following processes occur to stop the robot
safely:
1 The safety PLCfirst turns off the STOcontactors so power is cut from the motors.
To ensure that the STOcontactors switch states as expected, there is a feedback circuit
that connects to the safety PLC to verify that the contactors switch to the correct state.
When the robot is starting up, the feedback circuit and STOcontactors are checked
before allowing the robot to be operated.
2 The safety PLCturns off the SS1 contactors to activate the dynamic brake function in
the motors.
3 The safety PLCmonitors data from the motor encoders to determine whether the
robot has stopped within the expected amount of time.
4 Once the robot has stopped, the mechanical brakes are engaged to keep the robot in
place, similar to the parking brake in a car.
The mechanical brakes are only intended to engage when the robot has stopped. Only when the
dynamic brake function does not stop the robot within the expected amount of time are the
mechanical brakes engaged to stop the robot while it is in motion. This is considered an
emergency situation where the dynamic brakes have failed, and an error is reported in the robot
interface.