In this paper, a time-adaptation control for motion reproduction is proposed for adapting to variations of environmental location and toward advanced manufacturing process. The method has the highest priority on eliminating force error; by lowering the priority on time correspondence, the reproducibility of contact motion is improved. Concretely speaking, the proposed method matches the force response value with its command under contact motion, by introducing a difference between save time and reproduction time. By using this method, even when the environmental location is changed, it is possible to reproduce the same reaching velocity at the moment of first contact. Then, the force error in the reproduced motion is suppressed immediately. In recent years, not only production speed, but also product quality must be ensured in a manufacturing site. In an actual manufacturing site, because materials are natural objects, properties, such as the size of an object, are different in different lots. Therefore, a control method that can adapt to variations of environmental location is effective for achieving high-quality manufacturing.
The expansion of the applicable range of robots and machines requires the ability to cooperate with humans and adapt to external environments. It is necessary to use torque information in order to achieve these capabilities. A reaction torque observer is one of the effective methods to obtain torque information because it does not need a torque sensor and it can deal with torque information in the high-frequency domain. However, it needs a correct compensator to reject disturbances to estimate the precise torque. Generally, the disturbance compensator of the reaction torque observer is derived by manual model selection and manual/automatic parameter fitting. This method not only takes time and effort but also does not always obtain an optimal solution because it depends on a predetermined model. In particular, it is well known that nonlinear elements such as friction are difficult to model. To overcome this issue, an automatic design method of a disturbance compensator is proposed in this article. The compensator is abstracted automatically using an element description method. Using the element description method, model design in advance is not needed because the model selection and the parameter fitting are conducted simultaneously. Therefore, the element description method can be applied to systems whose model structure is unknown. In addition, it is possible to input human intentions as initial settings. These features enable designs that make use of human knowledge and the computational power of computers.
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