4. Control

4.1. Overview

Since the Robotiq 2-Finger 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 done 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 the Robot 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: 2-Finger control logic overview

4.2. Gripper Register Mapping

Register mapping

Table 4-1: Registers of the 2-Finger Gripper.

4.3. Robot Output Registers & Functionalities

Register: ACTION REQUEST

Address: Byte 0

rACT: First action to be made prior to any other actions, rACT bit will activate the Gripper. Clear rACT to reset the Gripper and clear 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 byte 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 motion is completed, the Gripper sends a fault signal and needs to be reactivated 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 85 mm or 140 mm opening respectively
• 0xFF - Closed
• Opening / count: 0.4 mm (for 85 mm stroke) and 0.65 mm (for 140 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 while in motion. If the current limit is exceeded, the fingers stop and trigger an object detection notification. Please refer to the Robot Input Registers & Status 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 & 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 (LED is blue)
• Priority faults (LED is blue)
  • 0x05 - Action delayed, activation (reactivation) must be completed prior to perfmoring the action.
  • 0x07 - The activation bit must be set prior to action.

Minor faults (LED continuous red)

• 0x08 - Maximum operating temperature exceeded, wait for cool-down.
• 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 : See your optional Controller Manual (input registers & 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

4.5.1. Force control

The 2-Finger Gripper gripping force is controlled via the rFR byte (refer to the Gripper Register Mapping 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 127 : Solid & fragile objects
  • Low torque mode
  • Re-grasp feature is on
• 128 rFR 255 : Solid & strong objects
  • High torque mode
  • Re-grasp feature is on

The table below shows the expected applied force according to the payload material hardness, speed setting rSP and force setting rFR. All tests were done with the 2-Finger Gripper with firmware GC3-1.3.9. Data was obtained with a Load Cell from Phidget, S Type, model 3138.

¹ Available with V-Groove fingertip AGC-TIP-205-0085 / AGC-TIP-421-140.

² Available with flat silicone fingertip AGC-TIP-204-085 / AGC-TIP-420-140.

³ HV refers to Vickers hardness test.

4 Durometer refers to Shore durometer hardness, scale A or scale OO.

Fig. 4-2: grasp force on hardness 220 HV (4340 annealed carbon steel).

Fig. 4-3: grasp force on hardness 95 HV (6061-T6 aluminium).

Fig. 4-4: grasp force on hardness 60A (silicone).

Fig. 4-5: grasp force on hardness 40 A (silicone).

Fig. 4-6: grasp force on hardness 10 A (neoprene).

Fig. 4-7: grasp force on hardness 30 OO (polyurethane).

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 movement when an object is slipping or dropped. When Re-grasping, the Gripper will attempt to close until it reaches the position (rPR) request.

• 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, gOBJ status will allow you to know if object retention was successful. This is a built-in feature for the 2-Finger 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.

Object detection exemple:

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.

Object lost example:

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

4.6. Control Logic

Fig. 4-8: Example of the 2-Finger control logic with associated registers.

4.7. Modbus RTU Communication

The Gripper can be controlled by Modbus RTU directly with RS485-RS232 using the ACC-ADT-RS232-RS485, or over USB using the ACC-ADT-USB-RS485. This section is intended to provide guidelines for setting up a Modbus scanner 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 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 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 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 C5 CE

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

4.7.4. Preset multiple registers (FC16)

Function code 16 (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 given in the Control Logic 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 grasp an object. It moves again to a second location to release the grasped 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 grasp is completed

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

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

Example of response if the grasp 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 grasped.

4.8. Control over TM

4.8.1. TM Robots Compatibility with Robotiq Grippers

4.8.2. Getting Started

1. Power ON the robot
2. Tap the triple bar icon in the upper left corner of the screen

3. Click on the Login icon in the navigation pane on the left

4. Enter your credentials and click on OK.

5. Click on Get Control

6. Click on the triple bar icon in the upper left corner of the screen and select Project

7. Click on the New Project icon in the upper left corner of the screen

8. Enter a name for your program and click on the OK button.

4.8.3. TM Gripper Components

Here is the list of the current Robotiq Gripper TM Components to install on TM Robots:

• GRIPPER_ROBOTIQ_2FIN85_V004_SET.Component = SET the Gripper (Speed, Force, Position)
• GRIPPER_ROBOTIQ_2FIN85_V004_GRIP.Component = CLOSE the Gripper (Action)
• GRIPPER_ROBOTIQ_2FIN85_V004_RELEASE.Component = OPEN the Gripper (Action)
• GRIPPER_ROBOTIQ_2FIN85_V004_CHANGEGRIPPER.Component = CHANGE the address of the Gripper/dual Gripper

4.8.3.1. Installation

1. Download the TM Plug & Play Software Package compression files on the official website
2. Unzip the file at the root of a blank USB storage device
3. Rename the USB storage device "TMROBOT"
4. Insert the USB storage device in the robot controller
5. In TM Flow (robot software), tap the triple bar icon and select System Setting

6. Select Import/Export

7. Click the Import button

8. Click on TMComponent in the Robot List window and click on OK

9. Click on the Component button of the Import navigation pane

10. Select the Components you want to import and click on the Import button

11. Tap the triple bar icon and select Setting to display the Robot Setting window

12. Click on the Component icon

13. Enable required Components in the Components list by ticking the radio button beside each of them

14. A Component that is enabled displays a green radio button; once the Components are enabled, click on the Save button

15. Create a new project or open an existing project, and locate the Gripper components in the navigation pane

4.8.3.2. Gripper Button

The user can assign Gripper Components to the Gripper button and use the latter to open and close the fingers of the Robotiq Gripper.

1. From the TM Flow homepage, tap the triple bar icon and select the Setting icon

2. Click on Gripper Button

3. In the Gripper Button window, tick the Using Customized Component radio button and select the Component you want to assign to either one of the Gripper actions

4. In the popup window, select or change the Component you wish to assign to the Gripper action/button, and click OK

4.8.3.3. Programming

SET Component

1. Drag and drop the SET Component icon after a program Gateway to place a SET program node (2FIN85_V004_SET1)
2. Tap the SET node to highlight it and click on the pencil to edit the settings

Fig. 4-9: SET Node Settings Menu

GRIP Component

1. Drag and drop theGRIP Component icon after a program Gateway to place a GRIP program node (2FIN85_V004_GRIP1)
2. Tap the GRIP node to highlight it and click on the pencil to edit the settings

Fig. 4-10: GRIP Node Settings Menu

RELEASE Component

1. Drag and drop theRELEASE Component icon after a program Gateway to place a RELEASE program node
   (2FIN85_V004_RELEASE1)
2. Tap the RELEASE node to highlight it and click on the pencil to edit the settings

Fig. 4-11: RELEASE Node Settings Menu

CHANGEGRIPPER Component

1. Drag and drop theCHANGEGRIPPER Component icon after a program Gateway to place a CHANGEGRIPPER program node
   (2FIN85_V004_CHANGEGRI)
2. Tap the CHANGEGRIPPER node to highlight it and click on the pencil to edit the settings

4.8.3.4. Changing the Modbus Slave ID

The user can change the Modbus Slave ID of a Robotiq Gripper via the Robotiq User Interface.

1. First, click on the Modbus RTU Parameters tab

2. Change the Slave ID of the Gripper by typing in the corresponding box
3. Click on the Apply button

4. Perform a power cycle (24 V) while the USB device remains connected.