ACTUATORS AND MECHANICS

Grippers

A gripper is a mechanical or robotic device designed to grasp, hold, manipulate, or transport objects. It serves as the “hand” or end-effector of a robotic arm or automation system, allowing the robot to interact with the physical world by gripping and releasing objects.

Types of Grippers

Parallel Jaw Grippers

Two opposing jaws move parallel to each other
Versatile for various object shapes and sizes
Precise control over gripping force
Ideal for packaging, manufacturing, and assembly lines
Can have soft jaws for delicate items or sturdy jaws for heavy objects

Vacuum Grippers

Use suction to handle flat, smooth-surfaced items
Effective for glass, plastic, and metal sheets
Common in food packaging, printing, and electronics production
Adaptable to various pad shapes and sizes
Some have sensors to verify grip security

Finger Grippers

Multiple fingers conform to irregular object shapes
Useful for bin picking and tasks requiring dexterity
Can have rigid or soft, compliant materials
Often equipped with tactile sensors or force feedback
Adapt grip based on object properties

Pneumatic Grippers

Use compressed air to control jaw movement
Known for speed and strong grip
Ideal for high-speed assembly lines
Common in automotive and electronics manufacturing
Come in various configurations (two-finger, three-finger, angular)
Durable for repetitive industrial tasks

Maqueen Mechanic Beetle

The Maqueen Mechanic Beetle kit transforms your Maqueen robot into a mechanical gripper system. This kit includes a metal gear servo, mechanical parts, and screws that allow you to add gripping capabilities to your Maqueen Plus.

The gripper resembles a beetle's mandibles, hence the name "Mechanic Beetle". This add-on enables your Maqueen to perform object manipulation tasks such as picking up, moving, and placing items.

Motion Constraints and Installation

When installing the Mechanic Beetle gripper, it's crucial to consider motion constraints:

Install the servo with the grippers closed and the servo programmed for 0 degrees. This ensures you have the full range of motion available and prevents potential damage to the gripper mechanism.
Carefully test the range of motion to determine the safe operating limits of your gripper. This protects both the gripper hardware and the servo from strain or damage.

Why is this important?

Understanding the motion constraints is crucial for several reasons:

It prevents damage to the gripper mechanism and servo by avoiding overextension.
It allows for more precise control of the gripper in your programs.
It helps in planning pick-and-place operations by knowing the gripper's capabilities.

Degrees of Freedom

The term ‘Degrees of freedom’ (DOF) refers to the range of motion of a mechatronic system.

The 2 common ways of describing this range of motion are:

the final motion (or desired motion) of a single part or the end effector
the total controllable motion across all parts of the system.

Watch this 2DOF motion simulation platform (1:03) to see an example of a system with 2 degrees of freedom.

The platform simulates motion felt by the driver of a racing car from its acceleration and cornering.
The platform rotates in 2 different directions using 2 micro servos.

Challenge 1: Range of Motion Test

Program a button on your micro:bit to increase the servo angle by small amounts with each press. E.g. From 50 to 55.
Observe the gripper's movement and note when it reaches its maximum safe opening.
This helps you understand the gripper's full range of motion and sets the groundwork for precise control.

from microbit import *

from maqueenplusv2 import *

init_maqueen()

pin0.set_analog_period(20)

# Example usage:

# pin0.write_analog(50)

# pin0.write_analog(100)

Challenge 2: Smooth Open and Close Functions

Create functions to smoothly open and close the gripper.
These functions should operate in a loop, providing a fluid motion for the gripper.
Consider using gradual increments for a more controlled movement.

Challenge 3: Precision Gripper Control

Measure the width of the gripper opening at its maximum amount
You will have previously noted the write_analog value to reach this maximum opening
Create a function that maps these values to mm. E.g. width_to_pulse
Modify your open and close functions to take an optional parameter width, which sets the gripper to stop at that width

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