Signal torque sensors

The distinction between a force sensor and a torque sensor is not clear, because in all cases a mechanical movement resulting from a force is converted into optical, electrical, or magnetic signals. This conversion defines the characteristics of the sensor. All sensors are made for limited ranges. 

A force sensor combines a structure that responds to force changes with a sensor that converts these changes into a signal. A torque sensor similarly consists of a torsion or tension element detector, but it also has to transmit the force. Consider the torque for a electric power steering system any failure would immediately mean loss of control of the vehicle, so this must be avoided under all circumstances. Steering column torque requires careful finite element calculation, durability and performance testing to failure, and validation. 

Electric power-assisted steering systems are more and more replacing hydraulic systems. To improve fuel economy, the power assistance is provided by an electric drive. Such a system only consumes energy when power is supplied, unlike hydraulic systems. A torque sensor in the steering column provides the input signal to the drive control unit. An example of an electric power steering system is shown in Fig. 7.12.4. 

Speed limits the ability to transduce applied force or torque for all measurement methods. Apart from electrical limits of filtering and signal conversion effects like material internal friction, skin effects and non-homogeneous material behavior will define speed limits. In most cases the rotational speed defines the principle of signal transmission. This is one of the reasons why torque sensors are still not used with automatic transmission. The input torque is calculated by the engine management [5],... 

The worst case is damping above the operational frequency. This means that the sensing element response includes a delay. For force and torque sensors there is no standard equipment on the market, as for electrical circuits. For signal transmission only radio-frequency based systems can avoid mechanical influences (Fig. 7.12.12). 

All automotive torque sensors form part of a system that could potentially lead to dangerous situations for the driver. Using incorrect signals that do not reflect the real torque must therefore be avoided under all circumstances. Various monitoring features within the sensors or the controllers are implemented. The data transmission from the sensor to the controller must fulfill these safety requirements, such that erroneous data transmissions are detectable. Another important... 

When a built-in self test is not feasible, we encounter difficulties because primary input signals cannot be easily provided within a standardized probe setup. To our knowledge, no commercial testing equipment is available that allows a set of primary stimuli like acceleration, pressure, torque, or mass flow to be applied to the transducer elements of sensor chips on the wafer level, with the required speed and precision. At the moment we are therefore left with purely electrical stimuli for testing microsensor devices. 

In order to have a reliable signal during different driving conditions, the NOx sensor must achieve good linearity Fig. 7.16.4 shows measurements with a conventional diesel engine dynamometer. The engine speed was varied from 1000 to 4000 ppm, the engine torque was varied from 50 to 200 Nm. Compared with a... 

This concept takes advantage of measured real-time feedback of AP and IE rotation from sensors on board the knee simulator. Based on those instantaneous AP and IE implant positions/motions, a real-time (or strictly, semi-real-time) computation is made of the influence/contribution of the desired soft tissue springs or any virtual mathematical restraint models. The computed AP force and IE torque contributions are added (vectorially, mathematically) to the electronic command signals for the externally actuated AP and IE torques of the simulator. 

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