tailieunhanh - Machine Learning and Robot Perception - Bruno Apolloni et al (Eds) Part 12

Tham khảo tài liệu 'machine learning and robot perception - bruno apolloni et al (eds) part 12', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 270 C. R. Wren to occlusion and they project 3-D information into 2-D observations yt 1 h xt i ỡt 1 The measurement process is also noisy. ỡt represents additive noise in the observation. The ỡt are assumed to be samples from a white Gaussian zero-mean process with covariance dt N 0 2 The state vector x completely defines the configuration of the system in phase-space. The Plant propagates the state forward in time according to the system constraints. In the case of the human body this includes the nonlinear constraints of kinematics as well as the constraints of dynamics. The Plant also reacts to the influences of the control signal. For the human body these influences come as muscle forces. It is assumed that the Plant can be represented by an unknown non-linear function f xt 1 f xt ut 3 The control signals are physical signals for example muscle activations that result in forces being applied to the body. The Controller obviously represents a significant amount of complexity muscle activity the properties of motor nerves and all the complex motor control structures from the spinal cord up into the cerebellum. The Controller has access to the state of the Plant by the process of proprioception ut c vt xt 4 The high-level goals v are very high-level processes. These signals represent the place where intentionality enters into the system. If we are building a system to interact with a human then we get the observations y and what we re really interested in is the intentionality encoded in v. Everything else is just in the way. A Classic Observer A classic observer for such a system takes the form illustrated in Figure . This is the underlying structure of recursive estimators including the well known Kalman and extended Kalman filters. The Observer is an analytical model of the physical Plant xt 1 txt Btut L t 5 The unknown non-linear update equation f from Equation 3 is mod- 8 Perception for Human Motion Understanding 271 0 Fig. Classic observer .