Integrated System Build & Test
Table of Contents
Team Vision for Integrated System Build & Test Phase
Planned to Complete
- Redesign and integrate extension mechanism drive system
- Assemble outer housing, electronics enclosure, and other mounting systems
- Assemble and test hydraulic system with valves and pressure sensors
- Integrate electronic system with hydraulic system and servomotor
- Test control of system via Arduino and control panel
- Debug Arduino operational code
- All except integration of redesigned extension
mechanism drive system
- Belt drive system has been designed, parts have been ordered, some modifications have been made ahead of receiving components
Panels for Outer Housing assembly were completed via water-jet cutting, allowing for system-level assembly of the following sub-assemblies and components:
- Extension mechanism (not driven)
- Flow manifold
- Electronics enclosure
- Release valve
- Hydraulics tubing
- Hydraulic pressure sensors
Extension Mechanism Drive Redesign
After the aftermarket aluminum long arm servo horn stripped while operating the servomotor, the decision was made to alter the approach for driving the extension mechanism. A belt-driven system was chosen due to simplicity and ability to be easily integrated into the system without major changes. Prior to this change, the extension mechanism was to be driven by a series of linkages, and only from one side, which presented multiple issues with binding of the extension mechanism and torque from the servomotor.
Note components in green. The small rounded-triangular component, located vertically between both idler pulleys that are attached directly to the extension mechanism, allows the belt to be spliced together, and moves with the belt to cause the mechanism to extend when the servomotor is rotated.
While building the full hydraulic system, the team reviewed the proposed layout for the system. In doing so, we realized that we would not need the original first valve whose job was to eliminate back flow into the pump. The pump supplies sufficient pressure to keep this from happening by itself. As a result, we were able to eliminate one valve from the system. A subsequent test verified our theory.
During the hydraulics test, we realized that when first priming the system, there is a lot of air present within the tubes. Some repositioning of the tubes was attempted to try to evacuate the air, but we are waiting to do testing in the tow tank and pool to see how the system behaves in regards to air in the tubes.
According to previous design review, the broken toggle switch had been replaced and re-soldering the wire had been completed which included power switch(ON/OFF), toggle switch (Pump/Valve) and other switch to control the servo motor. All switches had been tested and working full functionality as expected.
So far all the electrical components such as resistor, transistors and diodes had been soldering to the protoshield and wired instead of using breadboard. The protoshield had been testing with control panel, pump, vale, also with hydraulic system and test with gripper. All electrical working properly as desired. Most of Electrical parts almost done and ready to final testing at this point.
All electrical parts will be placed and tie properly in the water proof container to make sure no components moving during testing and the wire will be clean up for final testing.
Test Results Summary
Complete Actuator Assembly test
A full array of soft body limbs were fabricated and fitted to the flow manifold, The following criteria were looked at in this sub-assembly test:
- No ruptures or ejected limb bodies
- Even actuation between all limbs
- sustainable gripping force/pressure by the limbs
With the manifold assembly verified, integration into the rest of the system's hydraulic line was completed, and testing on system integration with the other sub-assemblies and valves were performed. The following aspects were components of testing:
- No leaks or unintended permeation of water throughout the hydraulic systems.
- Successful release of pressure via valve use.
- Ability to evacuate air from the hydraulic line, using the release valve.
- System-level check to gauge successful installation & operation of all included sub-assemblies.
Complete Hydraulic System with Pressure Sensor
The internal pressure sensor was tested inline with the gripper as it was being actuated. The above graph shows the rise of pressure over time. The sensor reports absolute pressure. The maximum gauge pressure reached within the gripper was 13.7 psi. Even though the gripper did not fail at this pressure, it appeared to be under undue stress at maximum actuation. Therefore, the team decided that 12 psi would be the target inflation pressure as the gripper was more than fully actuated at that pressure. 13 psi has been chosen as the absolute maximum desired pressure. When this pressure is reached, the release valve will open and deflate the gripper. Under normal operation, 13 psi should not be reached, but this second limit is being included for fail safe purposes.
Testing Control of Electronics with Control Panel
During this phase, the control panel and Arduino proto-shield were soldered and tested. Code bugs were discovered during this testing, and are currently being worked on. No electronic hardware issues have been found.
Actuator Assembly Grip Test
With completed assembly, integration and testing of the actuator subsystem, hydraulic subsystem, and controls subsystem, the gripping capability of the system was tested, to furher investigate the ability to adequately grab and secure objects of appropriate size. The follow aspects of the system were examined during testing:
- Successfully actuation around the target object
- Adequately even actuation between all limbs, such that the target isn't displaced.
- sustainable gripping force to hold the target object securely
- Reliable control of the pressure application and release via the control panel system