Subsystem Build & Test
Team Vision for Subsystem Level Build & Test Phase
Planned to Complete
- Fabricate all components for extension mechanism, manifold, hydraulic system, actuators, outer housing, and servomotor housing
- Wire and solder control panel, control circuits
- Waterproof electronics enclosure, servomotor housing, and pressure sensors
- Assemble and test hydraulic system actuation
- All fabrication minus the outer housing (water jet out of operation)
- Most circuits ready for operation
- Preliminary waterproof testing of electronics enclosure and servomotor housing
- Preliminary testing of hydraulic system and actuation of soft bending actuators
Waterproof Servomotor Housing
Waterproof Electronics Enclosure Modifications
In order to prepare the waterproof enclosure to hold the pump, electronics, and inlet and outlet tubes, a hole was drilled in each of two sides that corresponded to the pump inlet and outlet. Once the holes were drilled, cord grips were installed in the holes, and epoxy was placed in any open spaces around the grips.
Soft Bending Actuators
Pressure Sensor Waterproofing
Test Results Summary
The team was unable to test engineering requirements with official test plans at this point in the build phase, as we need integrated systems to do so. However, we did some preliminary testing for subsystem operation.
Sea-Flo Pump Testing & Limb Performance
Following previous testing to validate limb design, actuation ability, and successful water pump operation, testing was deemed necessary to confirm the water pump could be successfully utilized to actuate the soft-body limbs with water as the medium, rather than the previously utilized compressed air. Testing sought to achieve the following:
- Validate that the pump could output the required pressure in water flow
- Show leak-proof insertion and usage of the limb and hosing
- Confirm full and successful actuation of the limb under hydraulic force
Ruptured Hydraulic Test ResultsInitial testing using water to actuate proved unsuccessful. What actuation that was achieved is documented below. Notes for improvement from the rupture failure are as follows:
- Increase the thickness of the base layer which incapsulates the non-elastic material, and allow for a greater seperatiion istance betwen the internal chambers and the non-elastic layer.
- Implement controls in the pump's programming to cycle operation in a manner that allows for mitigated application of active flow
- Incorporate a physical pressure relief feature into te flow line of the hydraulic system, prior to its junction with the limbs
- Implement usage of a non-elastic material with better bonding/adhesion capabilities with the polymer. Ideal characteristics include fibrous or porous construction, while maintaining thin physical dimensions and robust strength.
Successful Limb Testing under Hydraulic ActuationFrom the above notes trials, the following key aspects of the improved tested limb are:
- 1A:1B DragonSkin Compound mixture with ~10% added thinning agent.
- Increased base layer thickness from 4mm to 7mm.
- Substituted in a new non-elastic material into the base layer construction. Was previously standard Gorilla duct Tape, New material is contractor's dry-walling tape.
Test was found to be successful, with full actuation achieved. Below is documentation of the trial. Next trial test is to incorperate the manifold block for flow control.Successful Hydraulic Limb Actuation Test Video
Preliminary Testing of Manifold & Limb Assembly
With minor modifications made to the limb's region which was to be inserted into the manifold (accounting for height thickness) the limb was able to be snuggly fit unto the flow barb-fitting. Testing with the manifold proved successful, with adequate actuation occurring in rapid time. From this test trial, the following items were noted:
- Limb was able to be successfully pressurized and actuated from the manifold configuration.
- No leakage or loss of pressure, due to the manifold's fitting, was observed.
- An equal degree of actuation was achieved as was during the previous trial
- Increased/prolonged pressurization distinctly added to the force of actuating grip
- The limb's path of curving, during actuation, should accommodate objects of various dimensions.
- Pressure and actuation position was easily maintained one the pump was turned off.
- Evacuation of pressure, at the end of the trial, was inherently forceful, signaling that the limbs should be able to easily return to a passively neutral state once the relief valve is activated.
Documentation of these observations, and the trial test are seen below.Successful Hydraulic Test of Manifold & Limb Assembly
Pressure Sensor TestingThe MS5803-14BA pressure sensor was connected to the Arduino Uno and tested. It was successfully able to report the temperature and pressure of the room to the Arduino. A barometer was used to verify its accuracy in the air. In the future, tests with water will be performed. In its current state it is fully soldered and properly encased in epoxy. Early next phase it will be tested inline with water.
SoftwareThe Arduino program to control the gripper has been largely finished. The software is ready for integrated system testing and debugging. Preliminary debugging and subsystem testing has accompanied the other tests during this phase. The program utilizes #defines such that the desired actuation pressure and maximum extension can be easily altered.
Servo motor testing with control panelServo motor had been able to turn by using control panel. On this particular servo motor it only can go up to 90 degree maximum angle. The result show servo motor operated on video below showed the servo arm controlled by control panel goes only up to 78 degrees which it’s not quite full 90 degree as expected and go back to original position. However after reassembly the mechanism inside the servo , now the servo arm can be able to turn from 0 degree to approximately 155-160 degrees which is more than need for this project. The extension mechanism only need to go up to 90 degrees to make a full extension and retract to original position.
Control PanelControl panel had been wiring to the switches. The issues after finish soldering the wire was one of the toggle switch broken. What happened was one of the pin on switch get hot during soldering, It’s led to short wire inside switch and make switch didn’t response. It will be replace soon. Otherwise The other switch working fine and will be demo with servo motor for mechanism extension.
Electronics Enclosure Waterproofing TestWith the modifications to the enclosure complete, inlet and outlet tubes were placed in the cord grips, and the pump was connected to the tubes. The container was sealed up, and placed just under water for about one minute. When it was opened back up, it was determined that no water had made it through to the interior. There was some moisture on the rubber seal around the perimeter, but the water did not continue any further. Further testing is needed to determine behavior at greater water depths and pressures.
Servomotor Housing Waterproofing Test
After the wire port was sealed with epoxy, the servomotor housing was submerged underwater to test for any leaks. It was lowered to just below the surface in a large beaker, and allowed to sit for approximately 1 minute. After pulling it out, the top plate was removed and the housing was inspected for any signs of leaking.
Some signs of water penetration were found in the area around the output gear of the servomotor, indicating some water is getting in around the servohorn. The servohorn will be tightened to further compress the o-ring, and marine grease will be added to the space between the servohorn and the servomotor to prevent any damage to the motor.