How to control 2-Finger Gripper via MODBUS RTU ?

Kenny 2017-08-20

I and using 2-Finger Gripper and I want to control its position, force speed using MODBUS RTU.

The gripper is connected to a Windows PC via a USB port and uses a USB to RS-485 converter.

I'm writing code in Visual Studio C++ and using boost library to connect to the gripper.

I follow the manual to control the robot.

Activation request: 09 10 03 E8 00 03 06 00 00 00 00 00 00 73 30

Closing the Gripper: 09 10 03 E8 00 03 06 09 00 00 FF FF FF 42 29

Opening the Gripper: 09 10 03 E8 00 03 06 09 00 00 00 FF FF 72 19

It all works just fine when closing and opening with full speed,full force.

But if I adjust the position, speed or force.It doesn't read the command and return nothing.

What command should I send to control position,speed and force ?

Etienne_Samson 2017-08-21

@Kenny you need to write registers byte 3, 4 and 5 respectively to change position, speed and force.

The output registers are listed in the manual, explaining what you can send to the Gripper, the input registers are also listed, explaining what you can read. You could use Modbus function FC23 to read & write, normally you would do this to write position X and get an echo of that position X. You can also do it with FC16 like you were doing with your example.

Michael_Perez 2017-08-21

Hi @Kenny,

Here the values you have to change depending of your application

louis_bergeron 2017-08-21

@Kenny

Don't forget to calculate the new CRC characters required at the end if you change any values in the command you send.
See here for Modbus CRC calculation:

http://www.simplymodbus.ca/faq.htm#CRC

Kenny 2017-08-21

@Michael_Perez, @Etienne_Samson , @louis_bergeron
Thanks , I appreciate your help. I know where my problem is. I was changing the value of position, speed and force but I didn't recalculate the CRC. No wonder there was no reaction. Now it works just fine. My sincere thanks for your help