Collision Detection Function (Detection Function of Robot Motion Error)
Detect the robot motion error from differentiation between desired speed and the actual speed (speed deviation value). Errors can be detected by this function is classified into A and B.
- A: Collision or contact of robot arm or hand occurs
- B: Robot motion errors other than collision or contact
Also, error B is classified into below according to the power condition.
- Error in high power
- B1: Torque saturation due to a low Weight or Inertia setting.
- B2: Torque saturation due to combined motion of multiple joints and movement of a long object.
- B3: Torque saturation due to supply voltage reduction.
- B4: Error motion due to hardware error or software malfunction.
- Error in low power
- B4: Error motion due to hardware error or software malfunction.
- B5: Torque saturation in low power due to a hand or a long object that exceeds the weight described in the specifications.
When an A or B error is detected, one of the messages below will be displayed and the robot will stop. Reduce the damage of the robot or equipment.
- Error 5057: detect the collision in high power. (Detect the robot motion error.)
- Error 5058: detect the collision in low power. (Detect the robot motion error.)
The following errors have previously existed; however, this function can detect the above errors quickly.
- Error 5042, 5043: Position error.
Error is not detected by torque saturation in short time. Detect a state with high risk that causes a malfunction and stop the robot. The following phenomena may occur if you continue to use the robot in B1 or B2 status. Make a state that errors do not occur.
- Loose binding parts such as screws.
- Reduction gear is damaged.
- Increase a risk of robot damage
Turn ON CollsionDetect command and detection is enabled. (Default: ON)
Default is different depending on the firmware version.
- Ver.7.2.1.x or later: default: ON
- Before Ver.7.2.0.x : default: OFF
- When upgrading before Ver.7.2.0.x or Ver7.2.1.x or later: default: OFF
Reboot a controller to return to the default.
The following describes the detail of error B when error 5057 or 5058 is detected without a collision or contact of the robot or arm.
In high power mode
Check the torque saturation by using PTRQ command. Torque saturation is occurred if the joint outputs "1" in PTRQ command. In that case, make sure that the Weight setting is properly and in accord with the hand weight. Also, make sure that Inertia setting is properly for joint #4 of SCARA robot and joint #6 of 6-axis robot.
Next, make sure that there is no torque saturation by using PTRQ command by combined motion that multiple joints (#2, #3 and #5 joints of 6-axis robot) operate in the same direction and throwing around the long object.
If torque saturation occurs, reduce acceleration/deceleration of Accel command until there is no torque saturation (the value: 1.0 or less is displayed in PTRQ).
Also, torque saturation may occur due to reduction of supply voltage that inputs to the controller. Check the power supply voltage is within the specifications.
You can turn ON/OFF the collision detection function per equipment if you want to use without performing those error detection due to equipment compatibility securement or similar reasons.
If other error occurs at the same time, take a countermeasure for that first.
In low power mode
Make sure that hand weight is within the specifications.
Also, check the torque saturation when errors occur on the joint #4 and 5 of 6-axis robot. When torque saturation is occurred, it is long object that cannot be hold by low power mode. Hold in high power mode.
If other error occurs at the same time, take a countermeasure for that first.
Immediately stop result of the torque saturation by combination of the following motion and command. Error of A and B can be detected faster.
- HP motion: LimitTorqueStop Command
- LP motion: LimitTorqueStopLP Command
The following describes details of collision of the robot arm A and contact detection.
For reduction of damage on the arms and the end effectors due to the collision with peripherals, there are two functions: Collision detection function, and torque restriction function described in the next section.
- The collision detection function detects the collision and stops the robot immediately.
- The torque restriction function restricts torque at the collision and also stops the robot immediately.
These are functions to reduce damage on the robot at the collision, but cannot avoid damage completely. Also, the functions cannot be used for the purpose of human safety.
As shown following, the force applied to the robot during a collision can be roughly divided into two types:
the impact of speed right before the collision, and the pressing force by motor torque after the collision.
The collision detection function and the torque restriction function reduce damage caused by the pressing force right after the collision. These functions do not have any effect on damage caused by the impact of speed.
| Symbol | Description |
|---|---|
| a | Impact force at speed |
| b | Pressing force with torque |
| c | Force |
| d | Time |
The collision detection function detects collision by the speed deviation value for robot motion control (differentiation between the desired speed and the actual speed) showing an abnormal value which is greatly different from normal motion due to the collision.
Turn ON CollsionDetect command and the detection is enabled. (Default: ON)
Default is different depending on the firmware version.
- Ver.7.2.1.x or later: default: ON
- Before Ver.7.2.0.x : default: OFF
Reboot a controller to return to the default.
When enabled, this function reduces the time of pressing force by the motor torque, by detecting the collision and stopping the robot immediately. This reduces the pressing force by about 20%. To reduce the damage more, use this function together with the torque restriction function.
This function is automatically disabled during the pressing motion and the force sensing operation described in the following.
Also, the function may have false detection in cases of powerful contact motion and significant acceleration and deceleration which may have consecutive torque saturation. To confirm if there is a risk of false detection, use PTRQ.
If PTRQ is less than 1 for all axes, there is no risk of false detection.
If PTRQ is one, torque saturation is occurring on the axis. This means excessive acceleration and deceleration are applied, and it is not preferable for motor control. It also has a risk of damage on the manipulator. In such a situation, take the following countermeasures.
For contacting operation,
- Lower acceleration and deceleration at a contact
- Set a contacting depth shallow
If you want to operate the manipulator without taking the above countermeasures, you can enable and disable the function for each axis. Set the function off for the axis which you want to disable the function.
For details of the command and function, refer to the following manual.
"SPEL+ Language Reference - CollisionDetect, CollisionDetect Function"