tailieunhanh - InTech-Climbing and walking robots towards new applications Part 8

Tham khảo tài liệu 'intech-climbing and walking robots towards new applications part 8', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 210 Climbing Walking Robots Towards New Applications Biological Reflexes are neuronal mechanisms which transform sensory input into motoric action - often with using one or more interneurons. The motoric action depends mostly on the strength of the stimulus and the interneuron circuit. In contrast to the common assumption that reflexes are fixed reactions it is possible that interneurons can be reprogrammed and thus change the motoric action Reichert 1993 . In addition the occurrence of reflexes is often sent to higher neuronal centres. Therefore a simple reflex model has an input- activation- and a response-function see Fig. . Furthermore the reflex can be controlled via control signals from higher levels . the threshold can be changed to weaken the reactivity of the reflex in certain states. In the lateral walking for example a stumbling correction reflex Forssberg 1979 which is reasonable and found in forward walking would not work appropriately or produce an adverse behaviour. Therefore this reflex should be inhibited during lateral walking by applying proper control signals. Fig. 15. Reflex model The control signals Cl are given from the outside see Fig. . The response function r t is activated when a f t is positive and is responsible for the reaction of the controlled motor-joint s . An example of the reflex is the well-known tumbling correction reflex implemented in the SCORPION and ARAMIES Spenneberg 2006 robot. This reflex and corresponding data can be found in Spenneberg Kirchner 2001 . It is only active in the first two thirds of the swing phase of a leg. If the leg hits an obstacle a response is triggered which lifts the legs higher up to overcome the disturbance. In the stance phase this response is not triggered when the leg is disturbed. The input for the input function is the current drawn by the shoulder motor which drives the leg forward thoracic joint of the SCORPION . Because of the low load on the leg in the swing phase the threshold is .