Testing - Power Signal, Component, and Prototype

Power Signal Design

In order to control the time it takes to move the actuators the required (2) millimeters, the team needed to control the rate at which the voltage was applied to the actuators. The team accomplished this by creating a piecewise sinusoidal signal that would apply the required 500  voltage over the time periods that was calculated in the previous section. The modified signal that was created can be broken into four sections which represent the four moves the actuators make before returning to their original resting position. 

The angular frequencies of the sine functions were set to create a  change over the specified time periods. The two larger sections represent the set-up strokes; the longer time to make the move means that there’s a lower force output. The two smaller sections represent the power strokes and are 10 times smaller than the set-up strokes.  This signal is what will allow the robot to move through a high viscous fluid and still generate an unbalanced force.


Component Testing


Before assembling the robot, the team first tested the actuators to ensure that they were in good working order and without defects. This would ensure that the testing would yield useful results, since any defect in the actuators would compromise the test runs. To carry out the testing the team used the micro-materials laboratory to set up a work station.

The team used a programmable function generator to store the modified sine signal. A laptop with proprietary software from the function generators manufacturer was used to load the teams modified sine-wave onto the generator. Once loaded, the team could adjust the overall period of the function while still maintaining the 10:1 ratio between power and set-up strokes. This allowed the team to fine-tune the actuators operation to achieve the resonance state required to achieve the maximum deflection. This was necessary because piezoelectric actuators have inherent error in their operation. 

This signal was then split, with one feeding an amplifier to generate the necessary 500  signal required to drive the actuators. The other signal went to an oscilloscope that was used to verify that the output from the function generator had the necessary time delay for each segment, allowing us to confirm that the function generators signal was good. 

Finally, the output from the amplifier was connected to an actuator allowing us to visually inspect the actuators operation. This allowed the team to ensure that the equipment and actuator were working properly before assembling the final model and beginning testing. 

Final Model Testing

The prototype was constructed and tested in the silicone oil with the density and viscosity required to mimic the conditions at a microscopic level. However, when activated the prototype didn’t move, no matter what length of time we allowed the actuators to run for. The team tried to increase the surface area of the tail to increase the force output and well as decreasing the sine-waves period to allow for a higher force output. These were to no avail as all the adjustments made no difference to the robots performance. The testing proved that this conceptual model will not work at the microscopic level and that there are forces at work which the team did not account for which affected the prototypes operation.