The system for measuring torque, temperature control, and recirculation force on the HVAC unit uses a pair of measuring heads. One of them is used to control the rotary temperature and exhalation regulator; this head measures the control target to 2Nm. The second head is designed to control the recirculation rod. It generates a linear motion and measures the actuating force in the range up to 200N.
DC motors with planetary gearbox are used for control, which, unlike stepper motors, do not generate speed or force shocks. The rotation speed is controlled by a PWM signal of variable alternation and constant amplitude. The conversion of the rotary motion to the linear motion is carried out utilizing a precision nut bolt.
The measuring system allows the controls to be set to the selected position at the selected speed. For this purpose, each measuring head is equipped with a contactless position sensor (or angular position) based on the incremental encoder principle, which gives the best repeatability and precisely defined sensitivity in comparison with the other principles.
The measuring system consists of CANSAS modules for measuring bridges (force and torque), incremental position sensing, and PWM signal generation. All modules are interconnected via CANbus. The busDAQ module is also connected to this bus. This microprogram mainly provides:
- Feedback control of the position.
- Continuous measurement of force and torque.
- Their comparison with specified limits.
The busDAQ module is connected to the LAN. The client computer runs a program designed for entering the measurement sequence, controlling the measuring heads, and presenting the results, including printing the report. The program is prepared in the TestPoint development environment.
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