Dynamically walking robots require attitude sensors of high resolution and wide-band frequency response. If these characteristics are not good enough, it is difficult to control the robots stably. Rate gyros are widely used attitude sensors in walking robots, but the rate gyro which has both characteristics of sufficiently high resolution and wide-band frequency response is heavy and expensive. Therefore, the authors tried to get a small, light and low-cost rate gyro which has excellent

more »

... ristics both in resolution and response frequency by using multiple sensors and subtraction type of filters. In this paper, first, a method to expand response frequency of rate gyros without reducing their resolution and an idea of subtraction type of filters which are useful for expanding frequency range are presented. The subtraction type of filter means the filter that has a transfer function obtained by subtracting another transfer function from 1(unity). This filter provides flat response after composing two signals whose response frequency ranges are different each other. In this case, one is a signal obtained from a rate gyro whose resolution is high enough but response frequency is low, and the other is a signal obtained from a rate gyro whose resolution is low but response frequency is high enough. If we use an inclinometer together with rate gyros, we can sufficiently decrease zero-drift of gyros, because the inclinometer senses angular displacement by referencing gravity direction and its zero stability is high enough. However, the inclinometer is influenced by horizontal acceleration. This means that we have to use a low-pass filter whose cutoff frequency is extremely low to eliminate signal component induced by horizontal acceleration. Attitude sensor using two rate gyros mentioned above and one inclinometer showed good characteristics concerning zero stability, resolution and response frequency range.