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Safety Board Configuration

Overview

The robot is equipped with an Emergency Management Unit (EMU). It is a system that takes control of the robot's components as well as its power in crisis situations. It is indispensable in cases when work is carried out on the software of the device and therefore it is not yet stable enough. The EMU can stop the robot's movement, turn off the power of the user's device, or even turn off the entire robot, if so configured. Switches placed on PCB inside the robot allows you to adjust the robot's behavior to meet the relevant requirements. EMU provides also dedicated electrical User Safety Interface (USI) led out to the User Space.

Please take this document seriously. Inadequate and irresponsible setting of the unit may cause damage to the device, the workplace and people in the vicinity.

EMU signals

The EMU consists of a series of inputs (Triggers and Resetters), several outputs (Actions), a latch coupled to the reset circuit and switches for configuration. In the document below you will find a simplified structure, description of operation and instructions on how to proceed in specific situations. The default setting of the switches can be found in the chapter DIP switches at a glance

E-stop signal and the latch

The EMU operation due to the appearance of the appropriate trigger, we are calling the activation and latching of E-stop singal - the most important signal for this unit. The configuration of the unit allows for some changes in the way this signal is activated, the effects it brings and the method of resetting the latch of this signal.

Structure

The simplified operation of the unit is presented in the diagram below. The individual segments of the scheme are discussed later.

safety board logic

Triggers

CPU watchdog

The internal computer that transmits commands and information between the motors controllers and the rest of the system, constantly communicates with the EMU as well. When this communication is interrupted, the EMU will take some actions.

  • First of all motors drivers will be stopped immediately
  • E-stop will by activated and latched.

Internal SBC E-stop signal

The process responsible for communicating with the EMU may stop broadcasting on request. Then the EMU will behave according to the selected settings of the switches S02 and S03, the same as in the case of a system hang.

Driver Fault

The BLDC motor controllers in the robot are high-power devices that have an extensive operation management system. The controller can be programmed to detect sudden spikes in torque, fluctuating control signal, limit current etc. and send an error signal that will be read by the EMU which will cause activation and latching of the E-stop signal. This operation of the EMU can be disabled with switch S01.

Emergency button press

The EMU is also able to detect when the Emergency button (E-btn) on the robot is pressed. In this case, the E-stop signal will be activated immediately and will be latched. Additionally, another action can be performed, which is immediate power off of the robot, if switch S07 is turned on. This functionality is sometimes required, but it also has undesirable effects. Remember you will no longer have control of the robot that loses its power completely before restarting it.

User E-stop trigger input

The connector inside the robot can be used to trigger and latch the E-stop signal. For this purpose, voltage in the range from 3V to 12V should be applied to the appropriate terminals.

Resetters

There are two steps to deactivate the E-stop signal described below. The order does matter. Both conditions can be modified with switches S04, S05 and S06.

e stop latch resetting

First condition - Emergency button reset

The first condition necessary to turn off the latched E-stop signal is to reset the Emergency button (E-btn) on the robot. If the E-stop was triggered in another way than with E-btn, and E-btn is already reset, press it and reset it again.

Alternative to first condition - User E-stop input reset

The same function that resets the latch can be performed by User E-stop input. Only when switch S06 is on. Then switching the User E-stop input signal on and off will act as a necessary condition.

Second condition

Internal SBC E-stop reset

The signal is sent to the EMU from the internal computer only on request. It is the second of two conditions to disable a latched E-stop signal. Its function can be disabled with switch S04.

If the attempt to reset the latch by internal computer fails, e.g. due to the E-stop trigger signal presence or failure to meet the first condition, the computer will inform about it with an appropriate message depending on the attempt channel (SSH or WebUI terminal).

Actions

Turn Off Robot

Only triggered by pressing the Emergency button on the robot. Function activated with switch S07. If you want to use this function on your robot, please consider turning on S06 or turning off S05 to allow the latch to be reset by other means.

Turn Off AuxPwr

Activating the E-stop signal may disable AuxPwr high voltage power supply. To activate this functionality, turn on switch S08.

Wheel braking

By activating the E-stop signal, the motors will brake the robot.

SPDT relay

The connector inside the robot also contains the relay outputs with the Operating Open and Operating Close terminals, where the Operating state is defined when the robot is working properly. Turning off the robot or activating the E-stop signal in the robot switches the relay and closes the NO terminal and opens the NC connector. The maximum rating for these terminals is 1A @ 24V DC / 0.5A @ 125V AC.

EMU configuration

The following part describes the settings to suit the preferences of people working with the robot.

Access to DIP switches

To access the EMU configuration switches remove the rear deck. Read more how to.

safety board under rear deck

On the left side of uncovered space is placed the Safety Board with one eight-channel DIP switch.

safety board sw and connector

DIP switches at a glance

DIP SWActivated featureDefault
S01triggering the E-STOP from the BLDC driver.on
S02triggering E-STOP latch due to internal SBC crash.on
S03triggering E-STOP due to an internal SBC crash.on
S04the internal SBC condition for E-STOP latch reset.on
S05the Emergency button release condition for E-STOP latch reset.on
S06the User E-stop input as the E-btn release condition.off
S07immediate powering off due to E-btn hit.off
S08Aux power dependency on E-STOP.off

User Safety Interface (USI)

The SP1312/P9 socket, accessible from the user space side, is an electrical interface for EMU.

safety interface socket

It performs 3 basic functions:

  • You can use it to put the robot into the E-stop state.
  • You can use it to make other devices mounted on the robot go to the E-stop state at the same time as the robot.
  • You can use it to start and stop the robot remotely.

The schematic diagram of the electrical connection is presented in the graphic below.

safety interface electrical

User E-stop trigger input

Hardware input triggered by applying a voltage in the range of 3V to 12V to terminals 5 (+) and 6 (-) of the USI connector. It activates and latch the E-stop state on the robot.

SPDT relay output

The EMU is equipped with a mechanical contactor that changes its outputs depending on the E-stop state of the robot.

On the connector it has the form of physical 4 pins, the diagram of which is shown above. The maximum rating for these terminals is 1A @ 24V DC / 0.5A @ 125V AC.

A table below describes states of the outputs depending on the state of the robot.

StateOperating OpenOperating Close
Robot offConnected to CommonOpen
Robot on, operating normallyOpenConnected to Common
Robot on, E-stop activeConnected to CommonOpen

User Run trigger input

Trigger this input by applying a voltage in the range of 3V to 12V to terminals 7 (+) and 8 (-) of the USI connector.

  • When the robot is off, powering this input for 1 second will start the robot.
  • When the robot is on, powering this input for 1 second will start the shutdown procedure.