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Industry-SponsoreD Project
In industries such as robotics and aerospace, systems employ various motor-gearbox arrangements to carry out desired functions. Motors and gearboxes can be chosen to best meet the requirements such as rotational speed, precision, and torque.
Strain wave gearboxes are a type of gearbox which offer distinct advantages. This includes high reduction ratios in a compact volume, no backlash, and low complexity or part count. A common application of this gearbox type is in robotic arms, which makes full use of its advantages.
The gearbox components are typically metallic. There is an interest in polymer counterparts which has the potential to offer benefits such as weight reduction, cost reduction, and ease of mass manufacturing.
This project focuses on developing the tools to experimentally test strain wave gearboxes, to contribute to the development and evaluation of polymer components usage in such type of gearboxes.
The industrial partners for this project are Victrex, a high-performance polymers supplier, and Inovo Robotics, a robotic arms manufacturer.
PRACTICE SYSTEMATIC APPROACH
A systematic approach to solving the problem.
Project plan
Set out key objectives, deliverables, breakdown of activities
Literature review
Record various findings on a literature review matrix, building a better understanding of the different aspects of the problem
Agendas and minutes
Keeping track of regular meetings
Gantt chart
Timeline of activities, ensuring steady progress
Risk register
Idenify, plan for, and manage risks that may affect the project
Product Design Specification
List the requirements of the final product
Storyboard
Visualizing how the product will be used
GENERATE, EVALUATE, DEVELOP
The process leading up to establishing an economical and scalable test rig concept.
Initial ideas
Various ideas with different priorities
Pugh matrix evaluation
Ideas get evaluated in a Pugh matrix.
CAD assemblies
Moving on from sketches to CAD assemblies
Flowcharts
Outline the microcontroller program and the test rig's intended normal operating sequence
REVISED TEST RIG CONCEPT - KEY FEATURES
Building on the selected initial idea, the revised concept offers significant improvements in performance, flexibility, and capability.
Mass on an arm
Simple arrangement providing a known cyclic opposing torque for the motor-gearbox unit
Encoders
Collect positional data on the input and output side to be processed and analyzed
Mounting plate
Can be designed to accommodate various gearboxes, adding flexibility
Aluminium extrusion frame
Provides modularity and ease of manufacturing
Scalable concept
Industrial partners could simply scale up and swap in higher performance components e.g. encoders to meet their needs
Economical concept
Primary aim, to remain within the project's relatively low budget
Manufacturing
Manufacturing the test rig and the test subject.
TEST RIG
Once engineering drawings, STL files, and circuit diagram are finalized, parts can be manufactured.
Most components involved machining, others were 3D-printed.
The test rig is then assembled and wired. With the test subject mounted, some initial test runs took place.
TEST SUBJECT
Various options were evaluated for the test subject to verify the test rig concept. The options available include buying and testing an off-the-shelf gearbox, requesting a gearbox from industrial partners, or 3D-printing a gearbox.
It was decided to proceed with a 3D-printed gearbox for testing. In short, budget constraints ruled out the other options both directly and indirectly.
Key gearbox parameters had their respective justifications.
CONCEPT VERIFICATION
Successful testing, data collection and analysis would validate the test rig concept, meeting with the project's objectives.
POSITIONING TESTS
Test rig configured with a selected magnitude of opposing torque and inertia.
Positional data collected as the motor-gearbox unit executes positional commands.
The data is then exported to be processed, plotted, and analyzed.
The test repeats for different test parameters such as torque, inertia, speed, acceleration, etc.
STATIC STIFFNESS TESTS
Torque will be applied to the motor-gearbox unit incrementally.
The deflection data is collected.
The torque applied will be in both the positive and negative direction to achieve a full hysteresis curve profile.
CONCLUSION
Overall, the test rig was able to produce useful data for gearbox analysis in line with expectations, thus verifying the concept successfully.
There were shortcomings, mostly due to hardware, which limited the ability to definitively evaluate certain aspects like accuracy and precision.
Further work recommended on scaling up this concept to alleviate these issues and provide a stronger benchmark for future development and evaluation of polymer strain wave gearboxes.
Reflection
This project shared similarities with the previous project with Renishaw. I feel there were many skills I was able to practice and sharpen, for instance technical skills like CAD and design for manufacturing, as well as soft skills like communication and presentation.
This project brought about by Victrex and Inovo Robotics felt more open-ended. This presents a challenge by putting great emphasis on project scope management.
Looking back, my performance in the early stages were subpar. I was not confident and decisive enough. This occasionally affected the project's progress because of indecision. However, as the project progressed further, I did grew more confident and indecision became less of an issue. Reviews of the project's progress and structure later on indicated a need to revise certain elements, many of which were linked to the project scope. I soon made the necessary corrections and then presented them to the industrial partners for clarity and approval.
In the end, I am glad I was able to manage the project scope effectively. It was a nice recovery from deficiencies in the early stages and to finish strong with a successful delivery of the project, satisfying the industrial partners. Working on an industry-sponsored project, I am grateful for insight, advice and experience gained along the way.
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