Design and manufacturing of two DOF joint actuator using Harmonic drive

The equipment plan and software algorithms of Multi-degree of freedom robotic arm by using  2 Degree of freedom joint actuator using harmonic drive. An L-shaped joint will be designed with two actuators assembled perpendicular to each other that will provide us with 2 DOF mobility. The pur

Project Title

Design and manufacturing of two DOF joint actuator using Harmonic drive

Project Area of Specialization

Robotics

Project Summary

The equipment plan and software algorithms of Multi-degree of freedom robotic arm by using  2 Degree of freedom joint actuator using harmonic drive. An L-shaped joint will be designed with two actuators assembled perpendicular to each other that will provide us with 2 DOF mobility. The purpose using harmonic drive is to achieve zero backlash, high-capacity output bearing, high torque capacity, excellent positioning accuracy and repeatability, compact design, high efficiency, simple installation, and assembly. High speed and accurate actuation is achieved by using brushless DC motor so we will be using servo motors, as they are fast and precise. We will be controlling our joint by using Mach 3 controller and a Graphical User Interface (GUI) will be developed to control the motor. The project will be blocks based i.e., 1 block will add 1 DOF to the project and the joint (2nd block) with second block will output the 2nd DOF and so on. The basic idea is having the block-based structures to achieve additional DOF motion with adding additional blocks. The diameter of each block will remain the same, but the length of each block will be defined according to the task it has to perform. The project will eventually lead to an industrial grade manipulator. In phase one only 2 DOF links are being designed which can be replicated to make a multi-DOF robot.

Project Objectives

The actuator will consist of harmonic driven components mounted and housed by custom machined
aluminium parts. A frameless DC brushless motor directly drives a  harmonic drive, with the output
supported by a crossed-roller bearing. A power-on-to-disengage magnetic safety brake is included on the
motor rotor and is able to hold a torque at the output side, with all power removed.
This is critical to the operations strategy of Actuator, where the robot may have to hold limb poses for
long periods of time. Two-position sensors are included: an optical incremental encoder on the motor rotor
and a capacitive absolute position sensor on the actuator output.
Actuator electronics are mounted on the backside of the actuator and together with the mechanical components form the actuator assembly. The electronics
consist of a motherboard which hosts a servo drive for the drive electronics and a microcontroller to handle the brakes and actuator health monitoring. The servo drive and microcontroller communicate 

A limb consists of 3 elbow assemblies and an azimuth actuator connected to the body. An elbow contains limbs extended with inset showing a compact folded limb. two actuators paired orthogonally with connecting structure. Elbows are linked together with additional structure. Non-structural elbow caps cover the actuator electronics and allow easy access to the motor controllers.

Project Implementation Method

Modularity and reconfigurability are the two basic requirements of this system. This concept of modularity has been deployed in many engineering disciplines for a long time. It refers to dividing a complicated system into different modules with high portability, ease of maintenance. Modularizing system components can also decrease design and manufacturing time. From the mechanical structure perspective, a robot system is a collection of joints and links which are connected with each other to build a configuration that can perform a variety of tasks. Using modular joints and links, different configurations can be constructed, which is the concept of the reconfigurable robot.

Compact size and high power transmission capability are the two most important reasons why the harmonic drive (HD) is widely used by robot designers. Zero backlash is definitely one of the advantages of the HD, but the thin wall of the flex spline generates deformation when torque is applied, due to elasticity. Therefore, the stiffness of the flex spline largely affects the accuracy in motion control. The HD exhibits more complex dynamic behaviour than conventional gear transmission system.

Benefits of the Project

Harmonic Drive gears and actuators are used in a wide range of applications, each of which takes advantage of a different characteristic of the gear technology. Some applications depend on zero-backlash and high positional accuracy. Some require a high torque-to-weight ratio. Others depend on the unique configurations available. A few installations utilize all of these attributes.

Industrial robotics is one of the major application areas for Harmonic Drive gear components. These applications require zero-backlash gears with high torque capacity, high torsional stiffness, and excellent repeatability. Hollow-shaft designs also are favoured because they make cable routing easy, neat, and reliable. Gear units with high-capacity, cross roller bearings are sometimes selected due to their compact form and are particularly well-suited for use in the robot axis, which places significant tilting moments on the output bearing of the joint. The primary axes of six-axis robots must be capable of providing high peak torques during the acceleration and deceleration phases of a cycle. The primary axis gears must also exhibit high repeatability and high positioning accuracy to enable the robot to execute precise assembly tasks or accurate path-following applications, such as arc welding or adhesive application. Harmonic Drive gears and actuators routinely meet these demanding requirements.

Harmonic Drive gears reduce the inertia of the robot arm to improve dynamic performance through faster acceleration and faster settling time. They also increase payload capacity and reduce power requirements. Mobile robots have the capability to move around in their environment and are not fixed to one physical location

Technical Details of Final Deliverable

1.2 DOF L-Joint Actuator

Final Deliverable of the Project

HW/SW integrated system

Core Industry

Others

Other Industries

Manufacturing

Core Technology

Robotics

Other Technologies

3D/4D Printing

Sustainable Development Goals

Decent Work and Economic Growth, Industry, Innovation and Infrastructure, Sustainable Cities and Communities

Required Resources

If you need this project, please contact me on contact@adikhanofficial.com