tailieunhanh - Humanoid Robots Human-like Machines Part 3

Tham khảo tài liệu 'humanoid robots human-like machines part 3', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Multipurpose Low-Cost Humanoid Platform and Modular Control Software Development 71 current consumption on servo motors that is not a simple task and further on some insight is given about the process. Still on the proprioceptive sensors inertial perception is believed to be an advantage on yetto-come developments such as dynamic locomotion patterns. Integrated Micro-ElectroMechanical MEMS accelerometers ADXL202E Analog Device and a gyroscope ENJ03JA Murata were selected and even installed although they are not yet used to influence the system control. Finally for the extraceptive perception a vision system using a camera is to be mounted although it is not yet used for decisions. Measuring joint position Servos have internal position feedback which is physically accessible by reading the internal potentiometer used by the device controller. However a connection must be wired to the output of the encapsulating box. Besides the tree default wires for power and input PWM pulse a fourth wire is added to provide a voltage level between the power ground which is related to the potentiometer current position. The procedure applicable in both the Futaba or HITEC brands and possibly others is sketched in Figure 5. Figure 5. Wiring the servo to fetch the internal position feedback Conditions seem now to exist to obtain joint angular position except for the fact that voltage at the potentiometer output is not stable Indeed it depends on which part of the response to the PWM pulse the servo is at each moment. It was verified that the potentiometer output is only reliable during the duration of the pulse itself once the pulse finishes the servo internal controller enters the period of power application to the motor windings and interference will occurs as illustrated in Figure 6. A fine tuned software program had to be developed to perform potentiometer reading duly synchronized with PWM generation to ensure correct angular position evaluation. Input PWM pulse Figure 6.