This week we finalized our design for the motor module, as Deliverable 5 and the final presentation/packet were due at the beginning of Week 12 (December 5). We had officially decided on using an off-centered mass spun by a motor, and during class we discussed different placement options (i.e., at the ankle or mid-calf). We were also initially thinking about placing two motors on each leg; one on the lower leg and one on the thigh. However, we spoke to our tech adviser during the week and he brought up the fact that having two motors may cause issues. Unless the motors are perfectly in sync, then we might end up with undesired cancellation (or additive) effects.
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| Discussing placement options for the motor module on the thigh. |
We also did some preliminary calculations on the toque and power required for different frequencies and rotation weights, in order to help us determine what type of motor we'd need to order. Later in the week, Dr. Gordon let us borrow a motor and tachometer for testing. We wanted to spin an off-center mass and see if the results were as expected (meaning that our predictions for our actual motor would also likely be correct). We found the motor Dr. Gordon gave us to be too slow for our purposes. We borrowed an RC plane motor from a friend, and found that it was too fast; therefore we know that we want a motor that is somewhere in between the two sizes.
We were unable to spin a mass with the current set-up, however. We plan on mounting a motor to a wooden board sometime during the next week and repeating the test, as we feel as though this will be much easier than trying to hold the motor (and therefore, pose less threat of injury).
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| Jake trying to hold onto the spinning motor. |
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| Using the tachometer to measure RPM. |
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| RPM of the RC plane motor (~90 Hz). |
This week we also worked on Deliverable 5, the presentation, and the packet. The figure below shows our current plan for the whole body. We will detail the work done since the midterm and our future plans during the presentation.
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| New proposed scheme for the entire body, including elastic bands and the motor modules. |
We hope to order all of our parts before Christmas break and start constructing the prototype (and finishing critical module testing) immediately after Christmas break. This can be seen in the updated Gantt chart below.
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| Updated project Gantt chart. |
