ENERGY CONTROL AND SOFTWARE 189
Writing a software program to simulate coordination is a complex task. A good, firstorder approximation would be to write separate control algorithms for each component. For example, we can write one control loop for the arm and one control loop for the waist. While the control loop for the waist is rotating toward the wall, the control loop for the arm will recognize the optimum time to start moving the arm. It is possible to run into some trouble with many control algorithms running in parallel, but these difficulties can be overcome. Detecting and avoiding hazards, for instance, can become a problem. Moving one component at a time is more predictable because only one control loop is active at a time. If the waist and arm control loops are both operating at the same time, they must be coordinated if obstacles must be avoided. Coordination involves communication and falls prey to all the difficulties we discussed previously in parallel processing. If we watch the pitfalls, we can reap the rewards in energy savings. Another example of coordination involves the rotation of mass. Ice skaters pull in their arms when they go into fast spins. A robot that must rotate should pull in its arms before the rotation. Not only does it help avoid punching the operator, but also less rotational energy is needed. A good article on designing a low-power system is at www.iapplianceweb.com/ story/OEG20020623S0006, and a review of some of the electrical engineering techniques we’ve discussed can be found at http://academic.csuohio.edu/yuc/talks/ low-energy2k1021.pdf. Another interesting article can be downloaded from wwwhome.cs.utwente.nl/ ⬃havinga/thesis/ch2.pdf. The author clearly views the world in terms of energy. Table 3 in this article seems to indicate the average human expends daily the energy equivalent of a kilogram of coal, or roughly the energy in 10 beers. Check the chart out; it might explain some of the neighbors! Bottom line, the conservation and control of the robot’s energy reserves requires great care. Software algorithms, property written, can minimize the robot’s consumption of energy.