(1987-). We have been advocating the effectiveness of optical robot sensors since 1987, and we have demonstrated their effectiveness by using them in many prototype robot systems.

The fundamental principle is remarkably simple. Light sources, such as LEDs, and sensors, such as photo-transistors, are set opposite each other as in Fig. 1, and minute displacement can be detected with high precision by the sensors based on: (a) a light interrupting plate passing between them; or (b) a relative movement in position. If a four split sensor is used as in (c), two dimensional displacement may also be measured from the ratio of the amount of light detected in each part without dependence on the fluctuations of the characteristics of the LEDs. If an elastic body supports these light sources and light sensors, a force sensor may also be configured.

In the KORYU-II, the wheel axle is supported to produce minute displacement by the wire cut process as shown in Photo.1, and the horizontal force is detected by measuring the displacement optically. In the HELIOS-II and TAQT Carrier, a torque sensor is realized by supporting the ring gear of the planetary reduction device for the swing axle of the crawler in an elastic body as indicated in Fig. 2, and by optically measuring minute twists during torque transmission.

Photo.2 is a 3-axial force sensor which opposes a point light source to a four part photo-sensor and which measures the displacement in the direction of 3 axes from the changes in the amount of light.

Photo.3 is a 6-axial force sensor that utilizes a four-part photo-sensor and a light source unit in three frames. The structure is indicated in Fig. 3. A new method to correct the results of non-linear interference, which occurs in measurement, has been introduced into this sensor system. As indicated in Table 1, compared to the 6-axial force sensor utilizing a conventional strain gauges, such characteristics of this mechanism were found as: the precision is greater than in the past; the rigidity is the same as in the past; the device is an internally mounted amp model without using an externally attached amp; and the cost is about one column lower than those in the past.

References:

1. Shigeo Hirose, Kan Yoneda; Robotics Sensors with Photodetecting Technology, Proc. 20th Int. Symp. on Industrial Robots, Tokyo ,, , pp.271-278 (1989)
2. Shigeo Hirose, Kan Yoneda; Robotics Sensors with Photodetecting Technology, Proc. 20th Int. Symp. on Industrial Robots, Tokyo ,, , pp.271-278 (1989)