In this section the hardware and physical setup of the prototype robot will be discussed. State diagrams along with schematic diagrams of the hardware and the software structure will be illustrated.
The fundamental goal of the project is to develop an algorithm that mimics a naturalistic gait of a four-legged animal. The algorithm is to maintain the stability of the platform under any foreseen condition, that can arise in an unruly environment. This means the algorithm should meet following conditions:
Should be able to initially withstand external forces, that is, it opposes against any external force that threatens to destabilize it.
If external forces exceed stability, robot moves accordingly to compensate the force provided, by taking a step away from the direction of the force.
Balance based on pressure at bottom of feet of the robot using center of gravity concepts
What we plan to accomplish by the end of this project is to have a working model of the algorithm mentioned above. This involves:
The construction of a four-legged animal-like walking platform.
Mounting the appropriate microprocessor to the platform.
Attach the sensors, and hard-wiring them to the processor.
Finally we wish integrate the algorithm with the hardware that we constructed. This integration should be done in a way that allows for further improvements. Further more, the project should be presented in a way that makes it applicable for an end user to utilize the working model.
The objective of this project is to balance a four legged robot. The balancing is to be performed is software. It is for this reason that the physical design of the robot should not aid in its stability. All pre-existing walking robot kits have a reptilian frame. The legs protrude outwards from the side of the body and then extend to the floor. This design presents a wide base and in itself is very stable.
The robot for this project is built to have a typical mammal-like stance. This design will ensure that the legs will extend downwards and not outwards. Not only will this design reduce the size of the base, it will elevate the center of mass to make the robot even more unstable. As a result the robot will have an extensive dependence on the balancing algorithm.
The robot also requires a minimum of four legs to mimic animal-like walking. The reason for this is that one leg can be lifted for locomotion while the other 3 are sufficient to keep the robot balanced. It is also the objective of this project to allow for future gait changes. Having four legs allow for several variations in the gait, such as walking, crawling, galloping and the trot.
The architecture of the autonomous robot is as shown in the figure #5. The force sensors provide an analog voltage reading. This is converted to a digital format using the A/D in the PIC micro-controller. These values are manipulated and using timer control the servo angles of the knee and hip are changed. The PIC also communicates with the GUI using RS232.
The block diagram had many updates to it before its present state, along the course of the project. Please refer to the appendix for previous block diagrams. The block diagram shows the representation of how the software was developed.
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It's Going To Get Difficult Before It Gets Easier