P17027: Starfish Gripper
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Subsystem Build & Test

Table of Contents

Team Vision for Subsystem Level Build & Test Phase

Planned to Complete

Completed

Fabrication Results

Manifold

Final Machined Manifold Top

Final Machined Manifold Top

Final Manifold Bottom

Final Manifold Bottom

Extension Mechanism

Completed Extension Mechanism

Completed Extension Mechanism

Extension Mechanism with Manifold, Fully Extended

Extension Mechanism with Manifold, Fully Extended

Extension Mechanism with Manifold, Fully Retracted

Extension Mechanism with Manifold, Fully Retracted

Waterproof Servomotor Housing

Waterproof Servomotor Housing Bottom, with Motor

Waterproof Servomotor Housing Bottom, with Motor

Waterproof Servomotor Enclosure

Waterproof Servomotor Enclosure

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.

Cord Grips with Epoxy Seals

Cord Grips with Epoxy Seals

Soft Bending Actuators

Soft Limbs Assembled onto Manifold

Soft Limbs Assembled onto Manifold

Control Panel

Finished Control Panel Circuitry

Finished Control Panel Circuitry

Pressure Sensor Waterproofing

Pressure Sensor Encased in Epoxy for Waterproofing

Pressure Sensor Encased in Epoxy for Waterproofing

Battery Clips

Battery Clips

Battery Clips

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:

Ruptured Hydraulic Test Results

Initial 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:
Water Pump Test - Prior to Rupture

Water Pump Test - Prior to Rupture

Water Pump Test with Critical Rupture Video

Successful Limb Testing under Hydraulic Actuation

From the above notes trials, the following key aspects of the improved tested limb are:

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.

Full Limb Actuation under Hydraulic Actuation

Full Limb Actuation under Hydraulic Actuation

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:

Documentation of these observations, and the trial test are seen below.

Manifold Mounting Configuration - Passive State

Manifold Mounting Configuration - Passive State

Manifold Mounting Configuration - Full Actuation

Manifold Mounting Configuration - Full Actuation

Successful Hydraulic Test of Manifold & Limb Assembly

Pressure Sensor Testing

The 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.

Software

The 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 panel

Servo 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 Panel

Control 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 Test

With 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.
Interior of the Waterproof Enclosure for Test

Interior of the Waterproof Enclosure for Test

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.

Servomotor Housing Underwater in Beaker

Servomotor Housing Underwater in Beaker

Problem Tracking

public/Subsystem Build and Test Documents/ProblemTracking_SubsystemBuildTest.PNG

Plans for next phase

Individual Plans

Individual 3 Week Plans for Integrated System Build and Test Phase

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