Jamie Nichol and Dr. Paul Eastman, Mechanical Engineering
Creating an artificial biped (two legged machine) has proven a challenge. The first stage of the project, designing and building the mechanical frame, has required that I study several engineering disciplines. I have also learned many lessons by trial and error.
Initially I thought to design a machine that would mimic an animal in form. After some reflection, and a reminder from Dr. Eastman that this same approach severely delayed the success of the airplane, I changed my approach. I began to design a biped in a way that would both facilitate programming, simplify construction, and be inexpensive, without compromising functionality.
The design I arrived at is for a twelve inch tall machine with telescoping leg joints in place of knees. Eliminating the knee simplifies construction and programming. A telescoping leg does loose the collapsibility that a knee has. The extremely large ratio of retracted to extended length which a knee joint affords was unnecessary for this project. The telescoping leg is the most unique feature of this design.
The initial design has not changed significantly over the course of construction. However, I did change the design enough to necessitate scrapping of many completed parts. This change simplified the construction of the legs, decreasing the time it would have taken to complete them, even though I was required to start from scratch with the new design. This change also improved the mass distribution between the sections of the leg.
The most central part of this design is the foot. The sole of the foot is rubber impregnated webbing to which an aluminum plate is bonded. Between the aluminum plate and the rubber pad is a force sensing resistor which detects force concentration in the center of the foot. Above the aluminum plate is an “X” shaped polycarbonate plate which is supported at the four ends so that it can flex slightly. Strain gages are bonded to this plate. Signals from these strain gages ill be used to detect the position of the center of mass above the foot. The ankle is bonded to the center of the X.
Interestingly, a large amount of time has been spent encouraging the donation of equipment. Reluctance to contribute to undergraduate research is considerable. This reluctance has increased the time spent on this project, designing and building what might more easily have been purchased. I am fortunate that Cimtech Corp. and ORCA have contributed to this project.
As the pictures on the next page show, the mechanical portion of the machine is fifty percent complete. I had hoped to have finished the project by this time, but it seems I will be working well into 1998 before completion. The hundreds of hours invested in this project have given an amazing return. I have learned things I would not have learned without taking on this research. I look forward to finishing this project and publishing the results.