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DESCRIPTION
GENERAL MANUAL — MAR 18, 2022 — RELEASE: V1.0.0
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4 Description
4.1 General
The qb SoftClaw is a compact, light and versatile Variable Stiffness Gripper. It's able to grasp objects of the
most disparate nature, exploiting the
intrinsic mechanical
intelligence of its variable stiffness system,
without the use of any type of
sensors on
the contact surfaces or specific algorithms on the absorbed
current by the motors.
The custom-made electronic board inside the qb SoftClaw is composed of a logic stage for communication
and low-level computation, and a power stage for motion control. This, together with two DC motor and
its encoders, establishes a simple position and current control feedback regulated by a properly tuned PID
controller.
The qb SoftClaw does not use Common Industrial Protocols (CIP) or other industrial standards for I/O
communication due to historical design and technical reasons.
I/O data basically refers as measurements from the device, commands to the device, and parameters
from/to the device. These are handled in a custom package format as follows
2-byte — common preamble;
1-byte — target slave id;
1-byte — payload length;
n-byte — payload;
1-byte — checksum for communication integrity.
A custom-made single-master-multiple-slave (SMMS) serial communication protocol is implemented to:
send commands to the connected devices;
read measurements from the connected devices (motor position and/or current);
get and set configuration parameters.
4.1.1 Control Modes
The qb SoftClaw can be controlled by two
different modalities:
Position:
it is the control mode that most closely approaches the operation of a classic gripper. In this
modality the user can control both
position
and
stiffness.
The first parameter is used to set the
angular position of the qb SoftClaw movable arm, the second one allows the elasticity of the arm itself
to be adjusted. Higher values of stiffness indicates a greater rigidity of the gripper during the grasp;
on the contrary lower values allows soft grips.
Deflection:
it is the control mode that allows the user to regulate the grip force during the grasp. This
modality does not requires any type of sensors on the contact surfaces or specific algorithms on the
absorbed current by the motors, but exploits the mechanical intelligence of the qb SoftClaw. In this
modality the movable arm is controlled to close completely towards the fixed part for each
