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3. Collaborative Robot Safety (Undefined variable: MyVariables.ProductName)

Robot Testing and Safety Circuits Part Number: PF40-DI-00010 Rev. A

operation by both button and by stopping the robt by hand.

3. Power failure while the robot is moving. If AC Power is turned off while the robot is moving at

100% speed, a fail-safe brake on the Z motor is immediately applied to ensure that the robot does not

collapse under gravity. Note that for robot axes without brakes, this will result in a Category 0 (axes

without brakes can coast) E-Stop.

4. Encoder failure at any time. PreciseFlex robots use serial absolute encoders, which are checked

every 125 micro seconds for any data or checksum errors on the transmitted data. If eight data errors

occur in a row (1 ms), motor power is shut down. Communication errors are also checked before

allowing motor power to be enabled, and every 4 ms thereafter. If three communication errors occur

in a row, the robot is shut down within 12 ms. As either an encoder failure or a broken wire between

the encoder and controller will shut down the motor power, the encoder circuits are compliant with

CAT 3. TUV has verified this fail-safe operation.

5. Wireless pendant connection failure. It is possible to drive PreciseFlex robots using a wireless

teach pendant, which is in the form of a web server application, in manual mode from a wireless tablet

or laptop. In this case, a heartbeat connection is maintained between the controller and the wireless

pendant. If this heartbeat connection is lost, the robot will stop moving, but power will remain on

(Category 2 soft stop). For this test, the robot is moved under manual control using a wireless

pendant and the wireless router is unplugged. The robot should stop. While the wireless pendant

function supports an E-Stop, it is not recommended to use this function for a CAT 3 E-Stop as it is not

redundant, although the robot can also be safely stopped by hand. TUV has verified this fail-safe

operation.

6. Power amplifier Command or Amp fault. Both the total current command and the PID component

of the current command are monitored by a separate monitor task for saturation. If either of these

current commands saturate for longer than a specified time, a fault is generated and the motor power

is shut down. All motors except certain gripper motors in PreciseFlex robots are 3 phase brushless

motors. These motors require a rotating electrical field which must switch between the 3 phases in

order for the motor to turn. If a power transistor shorts to one of the power busses, only a single phase

will be energized. The motor will lock up and not turn. Because a shorted transistor in the power amp

cannot cause uncontrolled motion, this is a fail-safe situation and therefore CAT 3 compliant. This can

be demonstrated on the bench by applying DC power from a power supply across one of the motor

phases. If one of the motor leads is shorted to ground or another motor lead, the amplifier will detect a

fault and shut down within 10 micro seconds. TUV has verified this fail-safe operation.

7. CPU failure or software lockup. PreciseFlex controllers all contain both hardware and separate

firmware watchdog timers that must be refreshed every 4 ms by the software running in the CPU or

the motor power is disabled and the brakes are set. This circuit is both PLd and CAT 3 compliant. This

Brooks PreciseFlex 400 User Manual

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