Student Projects
Contact Information:
Country: Taiwan
Year Submitted: 2018
University: National Cheng Kung University
List of Team Members (with year of graduation): Yen-Chun Liu, Chang,Yu-Hsiang, Chao-Chieh Lan
Faculty Advisers: Chao-Chieh Lan
Main Contact Email Address: cclan@mail.ncku.edu.tw
Project Information:
Title: A two-degrees-of freedom robotic joint module
Description: A compact robotic joint module that can generate two perpendicular axes of rotation. Stepper motors and ball screw drives are used to achieve high torque-to-weight ratio and high efficiency.
Products:
Software: LabVIEW 2015, LabVIEW Real-Time Module, LabVIEW FPGA Module.
Hardware: NI cRIO-9039, NI 9401, NI 9237, NI 9264
The Challenge:
Industrial robotic manipulators have multiple degrees-of-freedom and high dexterity but they currently have three mechanical challenges. First, they are not reconfigurable. Their joints cannot be dismantled and reassembled according to the required application. Second, most robotic manipulators require harmonic drives for torque amplification. Although harmonic drives have very high gear ratio, they suffer from low power efficiency and rigidity when compared with other types of transmission mechanisms. Third, most manipulators use brushed or brushless DC motors that have low torque-to-weight ratios. This work presents a novel robotic joint module to solve the three challenges.
The Solution:
This module has two rotational degrees-of-freedom at the output. Two stepper motors are used as the actuators. Stepper motors were chosen because they have much higher torque-to-weight ratio. Encoders are attached to the end of the stepper motors. With proper feedback control, stepper motors can achieve very smooth force and position control performance. They are very reliable and produce larger torque than brushed or brushless DC motors that are frequently used in robotic manipulators.
The output of each stepper motor is connected to a belt drive and then to a ball screw drive in order to provide linear motion. The speed ratio of the belt drive can be easily adjusted by changing the diameters of the wheels. The motors, belt drives, and ball screw drives are compactly arranged in order to minimize the dimension of the module. The use of belt drives and ball screw drives offer very high power efficiency and large force/torque amplification.
The linear outputs the two ball screw drives are connected to two different slider crank mechanisms. The cranks of the two slider mechanisms are connected to a parallel spherical mechanism to generate two rotational output (pitch and yaw. The spherical mechanism uses only revolute joints and hence has very high rigidity. Strain gauges can be attached to the coupler of each slider crank mechanism in order to measure the output torque of the joint module.
The joint module exhibits the motion like a human wrist. Multiple robot joint modules can be serially connected and reused to achieve different levels of dexterity.
Robotic joint module
Level of completion: fully functional
Link to vedio: https://drive.google.com/file/d/1ssPHqaSvfJpjLkT2GtD0-PRh-ElGFzVj/view?usp=sharing
