Skip to content

The gripper at a glance

The SSG-48 is a two-jaw parallel gripper driven by a brushless gimbal motor under field-oriented control. The Spectral Micro driver inside the body regulates the motor's current, so a move sets not only where the jaws go and how fast, but how hard they press: the current limit is the grip force, from about 8 N at 150 mA to about 80 N at 1500 mA. The jaws stop on an object, hold it with that force, and the driver reports that an object was found.

The SSG-48 gripper with pinch fingers
Figure 1.1: The SSG-48 gripper with pinch fingers.

The parts

Part What it does
GBM5208-75 gimbal motor the actuator: a brushless motor wound for high torque at low speed and low current
Spectral Micro driver, inside the body field-oriented control of the motor, the gripper state machine, the CAN and UART interfaces
Pinion on the motor, two racks on a linear rail the pinion turns, the two racks move in opposite directions: the jaws open and close symmetrically
MGN7 linear rail, 100 mm carries the two jaw plates; 48 mm of stroke
Jaw plates printed, with a four-hole pattern for your own fingers; fin-ray and pinch fingers in the repository
Thermistor in the motor windings temperature protection: the gripper stops at 75 °C
M8 4-pin connector 24 V and the CAN bus, one cable to the robot
Coupler connector mounts the gripper on the PAROL6 or PAR6 wrist, on a UR5 flange, or on your own with the template

The driver's status LED, its UART port and its CAN termination switch are inside the body, under the coupler connector.

What the firmware does

After power-up the gripper calibrates by finding both end stops. Then it takes move commands: a position from 0 (open) to 255 (closed), a speed from 0 to 255 and a current limit in mA. When the jaws stop short of the target with the current at its limit, an object is in the way and is held; when they reach the target, the position is held. Every answer carries the state: moving, object found while closing or opening, or at the position. The gripper stops itself on an over-temperature, an E-stop bit from the host, a CAN watchdog that runs out, and every fault the driver detects. How the gripper works and Errors and recovery have the details.

How it is controlled

  • CAN, 1 Mbit/s, on the same cable as the power: one message moves the gripper and is answered with its state. From a PC with the CANvas adapter, from a ROS 2 node, from PAROL6 or PAR6, or from your own controller. See Over CAN.
  • Python, the Spectral-BLDC library on top of CAN. See With Python.
  • Motor GUI in the browser: connect, calibrate, open and close, watch the plots. See Motor GUI.
  • UART, the driver's serial port inside the body: for configuration, and for a self-built gripper. See Over UART.

The MSG gripper is the SSG-48's successor: the same protocol and software, with a stepper and the STEPFOC driver, three rail lengths and a camera mount. Programs written for one run on the other.

Comments

Found a mistake on this page? Edit it on GitHub · Report it · Get help · This page as Markdown · llms.txt · The whole manual as PDF