Control torque sensors

SAS will be needed in future applications such as EPS, AFS, and SbW. These systems need a torque sensor to measure the steering torque applied by the driver in order to control an assisting torque. Hence a combination of SAS and torque sensor seems to be obvious. Products combining angle and torque measurement have been proposed (e.g., an opto-electronic angle and torque sensor for integration in EPS and EHPS systems [29]). 

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. 

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... 

In the case of a torque sensor for traction control, output torque can be calculated by the engine management system from engine data. But when sensor designs become simple, very robust, and highly accurate, measurement with sensors will have advantages over calculation. 

Viscometers are being increasingly used for accurate measurements on modern industrial paints, especially waterborne paints. Rotating viscometers with a concentric cylindrical geometry (Searle system. Fig. 9.1) are advantageous for paints. Precise thermostatic control is easily achieved because the outer cylinder does not rotate. The drive and torque sensor are combined to form a single unit with the rotating inner cylinder. 

Force sensors are most commonly used in aerospace, medical, and automation measurement platforms, while torque sensors are often used in process monitoring and control. Different types of force and torque sensors can be used together to improve the quality of measurement in manufacturing processes. 

The option of shear rate control in rotational viscosimeters makes it possible to detect shear rate dependent flow phenomena. Variants with high-precision motors and torque sensors are called rheometers and are used in research projects above and beyond the viscosimetry (see also 115, 17, 18]). In these instruments, other measurement systems besides the cylinder geometries are used, that are described in the following chapters. 

In computer-controlled machines, sensors continuously monitor the three parameters— rotational speed, axial pressure, and weld time—in addition to the weld penetration, weld or penetration veloeity, and interfacial torque. For reprodueible results and eonsistent weld strength, proeess monitoring is reeommended. Figure 14.24 is a sensor output traee obtained during welding ofpolyvinylidene fluoride (PVDF). Axialpressure and rotational speed were set at 4.3 MPa and 3500 rpm, respectively. 

Torque may also be maintained in a controlled strain rheometer such as shown in Figure 8.2.2 by using feedback from the torque sensor to adjust the motor velocity or position. However, control is typically difficult because of the sample response. Ideally one should include the viscosity of the sample in the control algorithm. Performance can be improved significantly by avoiding the sample and closing the feedback loop around a torque sensor on the motor, such as motor current to a dc motor (Michel, 1988). However, brush fiiction in the motor limits the lowest torque levels to 10 to 10- N-m. 

These drives are normally open loop (sensor-less) without encoder. For higher regulation, it is better to adopt a two-phasor control, such as a field-oriented control (FOC) or a direct torque control (DTC) drive. 

Afterburn Control. Afterburn is the term for carbon monoxide burning downstream of the regenerator this causes an increase in temperature upstream of the expander. Temperature sensors in the gas stream cause the brake to energize. This provides sufficient resisting torque to prevent acceleration until the afterburn is brought under control by water or steam injection. 

The vision of braking and steering by wire will demand new, extremely reliable sensors. Even in early implementations of steer-by-wire systems, in which manual control can override any system failure, more than one sensor is normally used for the sake of redundancy. Many of the sensor principles required are already established in the market, including steering-angle sensors (e.g., for vehicle dynamics control) and pedal-position sensors. Mechanical action or feedback control, however, will drive the emergence of torque and force sensors. 

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