4. Control

4.1. Overview

The Robotiq Hand-E Gripper is controlled directly via Modbus RTU using a RS485 signal. It can also be controlled via an optional Robotiq Universal Controller using an industrial protocol (refer to the instruction manual of the Robotiq Universal controller). The programming of the Gripper can be done with the Teach Pendant of the robot or by offline programming. The communication method used to control the Hand-E Gripper does not change the control logic or register setups described in the following subsections.

Since the Robotiq Hand-E Gripper has its own embedded controller, high-level commands, such as "Go to requested position" are used to control it.

Control using registers

The Gripper has an internal memory that is shared with the robot controller. One part of the memory is for the robot output; gripper functionalities. The other part of the memory is for the robot input; gripper status. Two types of actions can then be performed by the robot controller :

1. Write in the robot output registers to activate functionalities;
2. Read in the robot input registers to get the status of the Gripper.

The Gripper Register Mapping section will map the different registers used to control the Gripper or to read its status while theRobot Output Registers & Functionalities section will detail the output (write) register functions, and the Robot Input Registers & Status section will detail the input (read) register status. The figure below is a representation of the memory and the control logic of the Gripper.

Fig. 4-1: Hand-E control logic overview

4.2. Gripper Register Mapping

Register mapping

Table 4-1: Registers of the Hand-E Gripper.

4.3. Robot Output Registers & Functionalities

Register: ACTION REQUEST

Address: Byte 0

rACT

First action to be made prior to any other actions; the rACT bit will activate the Gripper. Clear the rACT bit to reset the Gripper and clear any fault status.

• 0x0 - Deactivate Gripper.
• 0x1 - Activate Gripper (must stay on after activation routine is completed).

rGTO

The "Go To" action moves the Gripper fingers to the requested position using the configuration defined by the other registers, rGTO will engage motion while bytes 3, 4 and 5 will determine aimed position, force and speed. The only motions performed without the rGTO bit are activation and automatic release routines.

• 0x0 - Stop.
• 0x1 - Go to requested position.

rATR

Automatic Release routine action slowly opens the Gripper fingers until all motion axes reach their mechanical limits. After all motions are completed, the Gripper sends a fault signal and needs to be reinitialized before any other motion is performed. The rATR bit overrides all other commands excluding the activation bit (rACT).

• 0x0 - Normal.
• 0x1 - Emergency auto-release.

rARD

Auto-release direction. When auto-releasing, rARD commands the direction of the movement. The rARD bit should be set prior to or at the same time as the rATR bit, as the motion direction is set when the auto-release is initiated.

• 0x0 - Closing auto-release
• 0x1 - Opening auto-release

Register: GRIPPER OPTIONS

Address: Byte 1

Register: GRIPPER OPTIONS 2

Address: Byte 2

Register: POSITION REQUEST

Address: Byte 3

This register is used to set the target position for the Gripper's fingers. The positions 0x00 and 0xFF correspond respectively to the fully opened and fully closed mechanical stops. For detailed finger trajectory, please refer to the Specifications section.

• 0x00 - Open position, with 50 mm opening
• 0xFF - Closed
• Opening / count: ≈0.2 mm for 50 mm stroke

Register: SPEED

Address: Byte 4

This register is used to set the Gripper closing or opening speed in real time, however, setting a speed will not initiate a motion.

• 0x00 - Minimum speed
• 0xFF - Maximum speed
•  

Register: FORCE

Address: Byte 5

The force setting defines the final gripping force for the Gripper. The force will fix the maximum current sent to the motor . If the current limit is exceeded, the fingers stop and trigger an object detection notification. Please refer to the Picking Features section for details on force control.

• 0x00 - Minimum force
• 0xFF - Maximum force

4.4. Robot Input Registers & Status

Register: GRIPPER STATUS

Address: Byte 0

gACT

Activation status, echo of the rACT bit (activation bit).

• 0x0 - Gripper reset.
• 0x1 - Gripper activation.

gGTO

Action status, echo of the rGTO bit (go to bit).

• 0x0 - Stopped (or performing activation / automatic release).
• 0x1 - Go to Position Request.

gSTA

Gripper status, returns the current status and motion of the Gripper fingers.

• 0x00 - Gripper is in reset (or automatic release) state. See Fault Status if Gripper is activated.
• 0x01 - Activation in progress.
• 0x02 - Not used.
• 0x03 - Activation is completed.

gOBJ

Object detection status, is a built-in feature that provides information on possible object pick-up. Ignore if gGTO == 0.

• 0x00 - Fingers are in motion towards requested position. No object detected.
• 0x01 - Fingers have stopped due to a contact while opening before requested position. Object detected opening.
• 0x02 - Fingers have stopped due to a contact while closing before requested position. Object detected closing.
• 0x03 - Fingers are at requested position. No object detected or object has been loss / dropped.

Register: RESERVED

Address: Byte 1

Register: FAULT STATUS

Address: Byte 2

gFLT

Fault status returns general error messages that are useful for troubleshooting. Fault LED (red) is present on the Gripper chassis, LED can be blue, red or both and be solid or blinking.

• 0x00 - No fault (solid blue LED)
• Priority faults (solid blue LED)
  • 0x05 - Action delayed; the activation (re-activation) must be completed prior to perform the action.
  • 0x07 - The activation bit must be set prior to performing the action.

Minor faults (solid red LED)

• 0x08 - Maximum operating temperature exceeded (≥ 85 °C internally); let cool down (below 80 °C).
• 0x09 - No communication during at least 1 second.

Major faults (LED blinking red/blue) - Reset is required (rising edge on activation bit (rACT) needed).

• 0x0A - Under minimum operating voltage.
• 0x0B - Automatic release in progress.
• 0x0C - Internal fault, contact support@robotiq.com
• 0x0D - Activation fault, verify that no interference or other error occurred.
• 0x0E - Overcurrent triggered.
• 0x0F - Automatic release completed.

kFLT

please refer to your optional controller manual (input registers and status).

Register: POSITION REQUEST ECHO

Address: Byte 3

gPR

Echo of the requested position for the Gripper, value between 0x00 and 0xFF.

• 0x00 - Full opening.
• 0xFF - Full closing.

Register: POSITION

Address: Byte 4

gPO

Actual position of the Gripper obtained via the encoders, value between 0x00 and 0xFF.

• 0x00 - Fully opened.
• 0xFF - Fully closed.

Register: CURRENT

Adress: Byte 5

gCU

The current is read instantaneously from the motor drive, value between 0x00 and 0xFF, approximate current equivalent is 10 * value read in mA.

4.5. Picking Features

As stated in previous sections, object picking is done via a simple "Go To" command, rGTO bit calls for movement, while rPR byte is the aimed position, rSP and rFR will be the desired speed and force settings respectively. This section describes key features in object picking applications:

• Force control
• Re-grasp
• Object detection
• Object contact loss

4.5.1. Force control

The gripping force is controlled via the rFR byte (please refer to the Robot Output Registers & Functionalities section).The Gripper behavior will change according to the rFR force requested.

• rFR = 0 : Very fragile objects or deformable objects mode
  • Lowest force
  • Re-grasp feature is off
• 1 rFR 255 : Solid & firm objects
  • High torque mode
  • Re-grasp feature is on

Measured grip force for steel of specific hardness (Vickers)

Coming soon

Measured grip force for silicone of specific hardness (Durometer)

Coming soon

4.5.2. Re-Grasp

Re-grasp feature is a built-in feature meant to prevent object lost due to slipping or inaccurate initial grip. The Re-grasp feature will allow the Gripper to initiate a movement when an object is slipping or dropped. When Re-grasping, the Gripper will attempt to close until it reaches the position request (rPR).

• This feature is automatically set according to the force request rFR.

• Re-grasp will keep the position setting:
  • Finger motion will stop when rPR position is reached, even if there is no object.
• Force and speed settings are not used, Re-grasp force and speed will automatically adjust to keep the object from being lost / dropped.

4.5.3. Object detection

When the Gripper grabs an object, the gOBJ status will allow you to know if contact with the object was successful. This is a built-in feature for adaptive grippers meant to be used by the robot controller (or PLC) commanding the overall application. The Object detection feature will change the gOBJ status and can be used inside your robot program.

As stated in the previous section:

gOBJ: Only valid if gGTO = 1.

• 0x00 - Fingers are in motion towards requested position. No object detected.
• 0x01 - Fingers have stopped due to a contact while opening before requested position. Object detected.
• 0x02 - Fingers have stopped due to a contact while closing before requested position. Object detected.
• 0x03 - Fingers are at requested position. No object detected or object has been lost / dropped.

Example of contact detected with an object:

1. Set position, speed and force at maximum (full closing):
   1. rPR == 0xFF, rSP == 0xFF, rFR ==0xFF,
2. Set ''go to requested'' will initiate movement :
   1. rGTO == 0x01
3. Then object detection status will be "in motion"
   1. gOBJ == 0x00
4. Until an object is picked, object detection status will then be "stopped due to contact while closing"
   1. gOBJ == 0x02
5. The user can now assume it is holding the payload, and proceed to the next step.

Example of contact lost with an object:

1. From the previous example, after an object is picked
   1. gOBJ == 0x02
2. If the gOBJ status displays 0x03 after it was 0x02, user can assume contact with the object has been lost.

4.5.4. Brake engagement

The Hand-E Gripper is equipped with a brake that engages at the end of each and every Gripper move, and thus disengages between each of these moves.

For instance, when fully closing on an object, the Gripper makes contact with the surface of the object and activates the brake before sending the object detection signal to the robot.

4.6. Control Logic Example

Fig. 4-2: Example of Gripper control logic with corresponding registers.

4.7. Modbus RTU Communication

The Gripper can be controlled by Modbus RTU directly with RS485 or over USB using the ACC-ADT-USB-RS485. This section is intended to provide guidelines for setting up a Modbus master that will adequately communicate with the Gripper.

For a general introduction to Modbus RTU and for details regarding the CRC algorithm, the reader is invited to read the Modbus over serial line specification and implementation guide available at: http://www.modbus.org/docs/Modbus_over_serial_line_V1_02.pdf.

For debugging purposes, the reader is also invited to download one of many free Modbus scanners such as the CAS Modbus Scanner from Chipkin Automation Systems available at: http://www.store.chipkin.com/products/tools/cas-modbus-scanner.

4.7.1. Connection Setup

The following table describes the connection requirements for controlling the Gripper using the Modbus RTU protocol.

¹ Various converters are available in the Spare Parts, Kits and Accessories section.

² These parameters can be adjusted using the Robotiq User Interface.

Each register (word - 16 bits) of the Modbus RTU protocol is composed of 2 bytes (8 bits) from the Gripper. The first Gripper output Modbus register(0x07D0) is composed from the first 2 Robotiq Gripper bytes (byte 0 and byte 1).

4.7.2. Read holding registers (FC03)

Function code 03 (FC03) is used for reading the status of the Gripper (robot input). Examples of such data are Gripper status, object status, finger position, etc.

Example of an FC03 read function:

This message asks for register 0x07D0 (2000) and register 0x07D1 (2001) which contains Gripper Status, Object Detection, Fault Status and Position Request Echo.

Request is: 09 03 07 D0 00 02 C5 CE

Response is: 09 03 04 E0 00 00 00 44 33

4.7.3. Read input registers (FC04)

Function code 04 (FC04) is used for requesting the status of the Gripper's analog input register. Examples of such data are Gripper status, object status, finger position, etc.

Example of an FC04 read function:

This message asks for register 0x07D0 (2000) and register 0x07D1 (2001) which contains Gripper Status, Object Detection, Fault Status and Position Request Echo.

Request is: 09 04 07 D0 00 02 70 0E

Response is: 09 04 04 E0 00 00 00 44 33

4.7.4. Preset multiple registers (FC16)

Function code 06 (FC16) is used to activate functionalities of the Gripper (robot output). Examples of such data are action request, speed, force, etc.

Example of setting multiple registers FC16:

This message requests to set position request, speed and force of the Gripper by setting register 0x03E9 (1002) and 0x03EA.

Request is: 09 10 03 E9 00 02 04 60 E6 3C C8 EC 7C

Response is: 09 10 03 E9 00 02 91 30

4.7.5. Master read & write multiple registers FC23

Function code 23 (FC23) is used for reading the status of the Gripper (robot input) and activating functionalities of the Gripper (robot output) simultaneously. Examples of such data are Gripper status, object status, finger position, etc. Action requests are speed, force, etc.

Example of reading and writing multiple registers FC23:

This message reads registers 0x07D0 (2000) and 0x07D1 (2001), which contains Gripper Status, Object Detection, Fault Status and Position Request Echo. It also sets the position request, speed and force of the Gripper by writing to registers 0x03E9 (1001) and 0x03EA (1002).

Request is: 09 17 07 D0 00 02 03 E9 00 02 04 00 E6 3C C8 2D 0C

Response is: 09 17 04 01 00 09 E6 F6 C1

Note that the content of the response might change depending on the Gripper's status.

4.7.6. Modbus RTU example

This section depicts the example from the Control Logic Example section, when programmed using the Modbus RTU protocol. The example is typical of a pick and place application. After activating the Gripper, the robot is moved to a pick-up location to grip an object. It moves again to a second location to release the gripped object.

Step 1: Activation Request ( clear and set rACT)

Request is (clear rAct): 09 10 03 E8 00 03 06 00 00 00 00 00 00 73 30

Response is: 09 10 03 E8 00 03 01 30

Request is (set rAct): 09 10 03 E8 00 03 06 01 00 00 00 00 00 72 E1

Response is: 09 10 03 E8 00 03 01 30

Step 2: Read Gripper status until the activation is completed

Request is: 09 03 07 D0 00 01 85 CF

Response (if the activation IS NOT completed): 09 03 02 11 00 55 D5

Response (if the activation IS completed): 09 03 02 31 00 4C 15

Step 3: Move the robot to the pick-up location

Step 4: Close the Gripper at full speed and full force

Request is: 09 10 03 E8 00 03 06 09 00 00 FF FF FF 42 29

Response is: 09 10 03 E8 00 03 01 30

Step 5: Read Gripper status until the grip is completed

Request is: 09 03 07 D0 00 03 04 0E

Example of response if the grip is not completed: 09 03 06 39 00 00 FF 0E 0A F7 8B

Example of response if the grip is completed: 09 03 06 B9 00 00 FF BD 00 1D 7C

Step 6: Move the robot to the release location

Step 7: Open the Gripper at full speed and full force

Request is: 09 10 03 E8 00 03 06 09 00 00 00 FF FF 72 19

Response is: 09 10 03 E8 00 03 01 30

Step 8: Read Gripper status until the opening is completed

Request is: 09 03 07 D0 00 03 04 0E

Example of response if the opening is not completed: 09 03 06 39 00 00 00 BB 10 30 E0

Example of response if the opening is completed: 09 03 06 F9 00 00 00 0D 00 56 4C

Step 9: Loop back to step 3 if other objects have to be gripped.

4.8. Control over Aubo i5

The Gripper Plugin package contains many features to program and control the Gripper. The package provides:

• Gripper node: The Gripper Plugin package adds a Gripper node that is used to add a Gripper command. A node can make the Gripper move to a specific opening, grasp an object and modify the speed and force applied by the Gripper.

4.8.1. Gripper Dashboard

4.8.1.1. Overview

Single Gripper

To activate the gripper:

1. Go to the Extensions tab on the top of the AUBORPE and go in the Gripper tab under Peripheral (on the left).
2. Enter the ID og the gripper (default for ROBOTIQ grippers is 9)
3. Connect to the gripper by pressing the Connect button
4. Press the Activate Gripper button to activate the button

To control the gripper independently:

1. Go to the Control tab (under Extensions tab)
2. It is now possible to set values for the position, speed, and force of the gripper as well as open or close it.

Fig. 4-3: Use interface to control the gripper independently

To control the gripper from the Programming tab:

1. To add a gripper node, go under the Condition tab on the left, and then press Peripheral
2. Press the Gripper button to add a gripper node
3. Press the Gripper node in the programming tree to set the values of position, speed and force.

Multiple Grippers

1. Plug one of the grippers to a computer using the USB cable
2. Open the Robotiq User Interface (RUI)
3. Connect to the gripper
4. In the Modbus RTU tab, change the gripper ID to something other than the default ID (default is 9)

Fig. 4-4: Modification of the gripper ID

5. Press apply, then refresh to apply the changes
6. Connect both grippers to the AUBO controller using the splitter
7. To activate the grippers:
   1. Go in the Extensions tab at the top of the AUBORPE

    

   

   Fig. 4-5: AUBORPE user interface

   2. Select the Gripper tab on the left and go to the Settings tab at the top
   3. Input the first gripper’s ID and press the Connect button
   4. Press the Activate Gripper button
   5. Once the gripper is activated, press the Disable Connect button to disconnect from the gripper
   6. Repeat these steps with the second gripper’s ID

   

   Fig. 4-6: AUBORPE user interface

   7. Select the Gripper tab on the left and go to the Settings tab at the top
   8. Input the first gripper’s ID and press the Connect button
   9. Press the Activate Gripper button
   10. Once the gripper is activated, press the Disable Connect button to disconnect from the gripper
   11. Repeat these steps with the second gripper’s ID
8. Once the grippers are activated, they can be used in programs:
   1. When adding a Gripper node to the program, simply input the ID of the desired gripper to control it

   

   Fig. 4-7: Using the grippers in programs.