Robotics Knowledge

In order to overcome the first two drawbacks of a gear mechanism, a com- mon solution is to use the pulley-and-timing belt assembly as shown in Fig. 4.19.In a pulley-and-timing belt assembly, the timing belt is a flex spline with teeth. The whole timing belt is normally made of soft material (e.g. rubber). The direct contact of the two pulleys is therefore replaced by the soft contact between the timing belt and the two pulleys. As a result, the effect of wear and backslash is not as serious as that of a gear mechanism. Since the length of the timing belt is selectable, it is easy to alter the distance between the input shaft and the output shaft. Just as with a gear mechanism, the speed reduction is equal to the ratio between the numbers of teeth of the two pulleys. If the number of teeth on the larger pulley is No and the number of teeth on the smaller pulley is Nt, the ratio of speed reduction (or the ratio of torque amplification) will be k - ^ Again, this ratio is not very high (t...

efer to Fig. 7.17 and Fig. 7.20. The output from a camera (either CMOS or CCD) is a continuous stream of images (video). In the case of a color Visual Sensory System of Robots 417 camera, however, the direct output from an imaging sensor consists of three streams of images: red component color images, blue component color im-ages and green component color images. If a camera's output has an analogue signal, the camera is called an ana-logue video camera. Output from an analogue video camera will be a con-tinuous one-dimensional signal, representing a stream of two-dimensional analogue images. This analogue signal is also called an analogue video. Digital cameras have been on the market since the late 1990s. Output from a digital camera can be a stream of two-dimensional digital images, called a digital video. If a digital camera outputs digital video, then it is called a digital video camera. As shown in Fig. 7.21, the computing hardware in a robot's visual sen- sory system is ...