Perspectives on the Human Controller: Essays in Honor of Henk G. Stassen

Perspectives on the Human Controller: Essays in Honor of Henk G. Stassen

Perspectives on the Human Controller: Essays in Honor of Henk G. Stassen

Perspectives on the Human Controller: Essays in Honor of Henk G. Stassen


Written in honor of Henk Stassen, one of the most prolific contributors to this research and literature, the book provides an up-to-date summary on human control of mechanical things. This includes people controlling the mechanical movements of their own limbs, extensions of their limbs such as prostheses (limb replacements), orthoses (limb braces), hand tools, or telemanipulators. It also consists of people controlling the mechanical movements of vehicles that they ride in such as aircraft, automobiles, and trains. Finally, it includes movements of discrete products through manufacturing plants, or chemicals and other fluids through process plants such as refineries or nuclear power stations. Within academe or industry, these various types of human control are usually found in very different research and engineering communities. The first is generally regarded as a subfield of biomechanics and more generally of biomedical engineering -- the hospital or medical clinic. Industry has mostly ignoredthe challenges of prosthetics and orthotics because there is not so much money to be made; payers are typically third party insurers of the government itself. In contrast, the problems of controlling vehicles (particularly aircraft and military vehicles) and industrial plants is what has driven the field of control -- both the science and technology. In the field of robotics, where biomechanics is obviously a model, industry has experienced the effects of expecting too much too soon, and in some cases over-investing and later being forced to withdraw in disappointment.


Jan C. Cool

There is need for well-designed appliances, particularly in the medical fields of rehabilitation and orthopedics. Common devices cry out for improvement, while many new instruments await development. Some essential strategies for new designs, based on mechanics, systems engineering, and human-machine interactions, are presented here.

There are three basics to design: a designer creates a concept, chooses its optimal forms, and selects appropriate materials. the designer unites the often conflicting features of these three fields. Obviously the choice of the right concept is the most important of the three.

In the conceptual phase engineers tend to design for function. in rehabilitation as well as orthopedics, this view has to be adapted to the very strong requirements set by Cosmetics, wearing Comfort, and Controllability. These three Cs describe the basic characteristics of subordinating function. Every anthropomorphic appliance at a minimum should harmonize with body contours, coordinate with normal body movements, and be controllable using minimal effort. Under these conditions prostheses and orthoses, internal as well as external, have to operate correctly, i.e., to be silent, reliable, and efficient.

2 Systems engineering

Prior to the design of a mechanical device, knowledge of systems engineering is necessary. the complete description of a physical system requires definition of both an over-variable, describing the physical quantity, acting as a potential difference over the system, as well as the through-variable, acting as a "flow" through the system. in mechanical systems, force corresponds to the flow variable and velocity (displacement) difference to the over-variable. According to Newton, force is considered to be the cause of acceleration and thus, in time, of velocity and displacement. For that reason the study of force configurations is essential for the conception of a design. the usual method of system description by displacements and rotations should be extended by a study of force attachment points, force action lines, and force configurations.

Familiarity with forces in every part of a system gives essential insight into the way the system operates. in the conceptual phase, a study of functional essential force patterns guides creativity and indicates force compensation and force control. a number of examples will be given for these three statements in the following sections.

3 Forces and creativity

Minimally necessary force patterns are powerful tools in creative engineering. the following three examples illustrate how thinking in total system equilibrium stimulates the generation of new conceptional designs.

3.1 shoulder orthosis

A lot of persons are handicapped by a functionless arm caused by a brachial plexus lesion or hemiplegia. in both cases often a painful shoulder joint subluxation is accompanied by . . .

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