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Control

Primary control interface for SSG48 gripper is CAN bus. Secondary control mode is with UART.

The gripper can:

  • Control the force, speed and position of gripper jaws
  • Movements of the both jaws are always in sync
  • Movement is initiated with a "Send_gripper_data_pack" command
  • Gripper has built in object detection feature that will report back when a object is detected

Go to Application interfaces tab for more details about the gripper commands!

The best way to learn how the gripper works is thru examples!

Working principle

  • After every power up the gripper needs to be calibrated to function.
  • Calling the calibration command will start the gripper movement. Calibration will find exact endpoints of the gripper.
  • After calibration the gripper needs to be activated.
  • After activation, gripper can be used (If there are any errors they need to be cleared also)
  • Now you can issues "Send_gripper_data_pack" commands that will move the gripper to the specified position with desired speed and torque presets.

The gripper will never send CAN commands on its own. Gripper will only respod to "Send_gripper_data_pack" with "Respond_Gripper_data_pack".

Empty commands

Note that Send_gripper_data_pack can be an empty command containg no data. The gripper will still respond to that with Respond_Gripper_data_pack. This options works great if you have a lot of devices on the can bus of the gripper and dont want to overload it with big data packets. The workflow here would be to send one Send_gripper_data_pack that contains the needed move and after that call Send_gripper_data_pack with no data to get responses from the gripper.

Command rate

It is recommended to send commands to the gripper with rate of 50Hz or higher!

Gripper GUI

You can install GUI from here!
To connect to gripper GUI you will have to have CAN bus adapter for PC.

drawing

  • Section 1 has a few commands important to operation of the gripper and connecting to it.
  • Section 2 has slider and entry boxes for commanding the gripper
  • Section 3 has shows gripper status
  • Section 4 shows current gripper position and current
  • Section 5 shows live plots of gripper position and current
  • Section 6 shows FPS of the GUI and options for dark/light mode

Note

Only one gripper can be connected to the GUI at the time.

Using the GUI

First you will need to know the COM port where your USB to CAN adapter is connected. After that enter it to the COM port box in section one. Press connect.

Default CAN Node ID

Default CAN Node ID is 0.

After you have connected to the GUI you will need to calibrate the gripper. Press the calibrate button in the section one. The gripper will start to move and if calibration was success you will see "Calibrated" in section 3.

Now that the gripper is calibrated press activate button and in case there is an error active press clear error button.

Now you can control your gripper by setting position, speed and current values in section 2.

Movement

Only setting the position value will start the gripper movement.

In the section 5 you will see live values of gripper position and current.

Using python API

This example will calibrate the gripper; after that it will open and close it. Note if the gripper is in error state you will have to first clear the error!
Get the API here!

import Spectral_BLDC as Spectral
import time

Communication1 = Spectral.CanCommunication(bustype='slcan', channel='COM41', bitrate=1000000)
Motor1 = Spectral.SpectralCAN(node_id=0, communication=Communication1)

var = 0

while True:


    #Motor1.Send_gripper_data_pack(0,255,1500,1,1,0,0) 
    #Motor1.Send_gripper_data_pack(255,255,1500,1,1,0,0) 

    if var == 0:
        #Motor1.Send_Clear_Error()
        Motor1.Send_gripper_calibrate()
        var = 1
    elif var == 1:
        Motor1.Send_gripper_data_pack(100,20,500,1,1,0,0) 
        var = 2
    elif var == 2:
        Motor1.Send_gripper_data_pack(10,20,500,1,1,0,0) 
        var = 0


    message, UnpackedMessageID = Communication1.receive_can_messages(timeout=0.2) 

    if message is not None:
        print(f"Message is: {message}")
        print(f"Node ID is : {UnpackedMessageID.node_id}")
        print(f"Message ID is: {UnpackedMessageID.command_id}")
        print(f"Error bit is: {UnpackedMessageID.error_bit}")
        print(f"Message length is: {message.dlc}")
        print(f"Is is remote frame: {message.is_remote_frame}")
        print(f"Timestamp is: {message.timestamp}")

        Motor1.UnpackData(message,UnpackedMessageID)
    else:
        print("No message after timeout period!")
    print("")
    time.sleep(4)

Using UART

To use uart you will have to acces UART port on the SSG48 gripper. Unscrew coupler connector and connect uart adapter to the connector on the image. Note that it uses 3v3, using 5V can destroy your driver/gripper. To read mode about how to use UART with SSG48/Spectral micro BLDC go to this link!

Setup:

  • Gripper 1 (Tells our motor controller we are using it as gripper)
  • Gripcal (this will calibrate the gripper)

Control:

  • Gripvel x (x is value from 0 - 255; 0 being min speed 255 max speed)
  • Gripcur x (x is value from 0 - 1300 [mA])
  • Grippos x (x is vale from 0 - 255; 0 being fully open 255 fully closed)

Note

Only Grippos will start the gripper movement!