Riley Smith
The ways in which the project will be tested include the use of a scale to measure grip force, as well as the use of various jigs to place the hand in in order to test the hand components in the scenarios described through analysis. The last method of testing the hand will include objects that the hand should be capable of grasping without the object slipping. Some of these objects will include a pop can or a softball. In terms of a testing environment the metallurgy lab (127) will be necessary for the stress testing that was previously discussed.
Using those test methods, the success of the hand is based on the ability of the hand to produce individual finger grip force. The success is also reliant on the hand being able to grip the specified objects and withstand the stress values described through the analyses done. The other testing requirements based on design requirements include that max load as well as the number of articulation points. The points of motion is simply a count, but another portion of data to collect is how much rotation the hand can travel from the designated rest position to the final grip position.
Some initial testing took place as the hand was being assembled. Two points on the hand failed, one was an error in press fit and the other was due to rubber band tension. The press fit failure was due to misalignment and too much pressure, which made one ear of an upper joint snap off. The other failure was the rubber band peg on the palm, since doubling and tripling up weaker bands was not an initial plan.
The first test ran on the hand was to determine the available grip force that the hand possessed. The minimum amount necessary was determined to be 13 ounces, in order to hold a soda can without slipping. The test was set up with a pound of hanging weight in order to enforce a safety factor of 1.2. The result of hanging a pound of weight and proceeding to make the hand move was that one finger’s wire broke free of the fingertip, and that the hand could not move from rest without assistance. The necessary assistance to allow the hand to move was to support the fingers so that they are level, then pull the wires. Also, the amount of force necessary to make the fingers lift is no longer 1.5 pounds, so the motors so move the hand must be stronger than initially determined. Based on this test, the changes necessary within the hand for success involve proper tying of the wires and a way to arrange the wires so that they become equal length for equal pulling. With equal lines the hand will proceed to operate evenly, which it did not during the test. The next test was to determine the new actual force required, so the new motors can be sized appropriately. The second test determined that the hand would be capable of gripping a can when 30 pounds of linear pull is used on the fingers. the test weight was 3.25 ounces to demonstrate the needed grip on each finger in order to grab the can. the final test was that the hand would be able to grab the can.
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Results:
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