Subsystem Build & Test
Table of Contents
Testing Procedure DevelopmentThe mechanical team has developed a test report procedure and format in preparation for sub-limb and sub-assembly build and verification. The mechanical test plan is detailed in the following report form, P7201 – Mechanical Range and Fit TR01. Fit and Range testing will begin as sufficient components and sub-assemblies become available for testing.
Manufacturing ProgressWe have been able to pivot all available resources in the RIT Machine shop to be able to facilitate an increase in throughput. This was done by creating a working relationship with all shop personnel, as well as, coming up with a loose schedule (by means of the Placker) to help the shop anticipate work that we will be expecting from the shop. This has allowed us to become more optimistic about completing the manufacturing portion of this project. This extended progress should have a compounding effect over the remainder of the semester as communication improves and other MSD order forms decline.
Outside of effectively engaging and using all shop staff, the team has been diligent in learning other techniques to increase productivity in the shop. This includes the use of Fusion 360 CAM software, allowing very rapid and precise machining programming to be generated to make complicated parts. This software, while requiring time to understand and use effectively, is an incredible force multiplier when faced with a high work load and rapidly approaching delivery dates.
CUI Interfacing TestOne of the CUI AMT-203 encoders was wired up and connected to a Teensy to test the SPI communication. Through SPI, the Teensy can get positional readings and set the zero-point position to be the current position. The process involves sending a command and waiting for a certain response that means the command is done. With the reading command, the next two messages are then the positional data. The exact commands and process are detailed in the datasheetEncoder status: The encoder is responding as expected. Positional readings change as encoder is spun, and have no drift when standing still. The zero-point command also works, and sets the current reading to zero. The datasheet says power cycling is needed before the new offsets take effect, but the zeroing has been happening consistently without power cycling. Up next is to make the code more robust (right now it blocks while waiting for the appropriate response) and to get the test bed set up with the motor to test the validity of the encoder.
Motor Operating Parameter StudyIn order to anticipate the approximate operating conditions of the Teknic Clearpath servos, calculations were done for primary joint velocities for a standard gait. Approximate angular displacements of joints were relative to that of humans and taken from an SFU lecture on angular kinematics. This provides a rough approximation of the speed at which the clearpaths must perform.
Ankle Motion Study
Risk and Problem TrackingThe mechanical team is in full-on manufacturing mode, leveraging various resources in and out of the RIT machine shop. At this stage, every custom-designed part has been scheduled with estimated manufacturing times. The updated Gantt chart below shows the mechanical manufacturing and assembly schedule for the next month and a half. Component manufacturing order is based on staged assembly of sub-limbs providing complete of sub-limb assemblies more than a month prior to ImagineRIT.
The Electrical team has completed Rev1 of PCB design and is submitting boards for fabrication. The following weeks consist of an extensive look at software implementation and hardware testing.