Navigation:  Tutorials > Measurement tutorials > Counter > DEWESoft 7.0  data acquisition, processing, analyzing and storage software Counters in automotive applications

We will look for two typical applications in automotive: steering wheel measurements and a wheel speed sensor.

 

Steering wheel sensor

In this case a measuring steering wheel a with quadrature encoder sensor is used to measure the angle position and the angular velocity of the steering wheel during test drives. The quadrature encoder used in our example has a resolution of 1800 pulses per revolution.

Channel Setup

Let's first set up the steering wheel sensor.

For the Counter mode, we should select the Sensor (encoder, CDM, tacho...) from the Basic application drop down menu to decode the signals of the quadrature encoder sensor and select the appropriate sensor (Encoder nn) from the Sensor type drop down menu . With Encoder mode the resolution of the angle measurement can be set. In this example "X1" is used and the counter outputs 1800 pulses per revolution. “X2” would output 3600 pulses per revolution and “X4” would output 7200 pulses per revolution. It is recommended to use an Input filter to avoid measurement errors caused by jitters or spikes on the signal (in this case 100ns). The quadrature encoder sensor normally has three signals. Only Signal A and Signal B are used for this application .

It is important that Encoder zero is not chosen if signal Z is connected to the counter input, else a jump in the frequency channel can appear and the manual zero point definition can be lost. The preferred way is to simply choose the sensor from the list, where all the scaling will be done automatically for us. The Encoder zero has to be de-selected and Reset on start measure should be so as de-selected not to lose the initial zero point correction.

 

The first output is the angle, where we can select degrees as units (this could also be revs or counts) and the second output is the frequency, which is already scaled in RPM or Hz.

Zero Point Definition

After all the settings in the channel setup are made, the steering wheel has to be set to zero for a specific steering angle. In most cases the steering angle is set to zero while the car drives straight ahead. Zero definition can be done by pushing Reset in the channel setup. This way, the steering angle is set to zero in that steering wheel position. A horizontal test track is recommended for the zero point definition to avoid a steer angle offset error. It is very important that Reset on start measure is not selected, else the counter value is set to zero at every measurement, and thus the zero point definition will be lost. The figure below shows the measurement results of the steering wheel.

 

 

Wheel speed sensor

The wheel sensor is used for high precision wheel speeds and rotations at test drives. We can also measure traveled distance and speed, but for this we need to know the dynamic wheel radius. The wheel radius, however, depends on the operating state of the wheel, e.g. road condition, driving conditions, cornering ability, tire pressure and other factors. Therefore a precise distance measurement with dynamic wheel radius scaling is not recommended. Instead, we could use either a GPS solution like VGPS or radar/optical sensors.

 

Again, we need to set the channel setup for the wheel sensor. This sensor is not defined as standard in DEWESoft, therefore we need to create it with the Counter sensor editor.

 

After the sensor is created, it just has to be selected in the sensor editor.

The angle output can be set to revs, degrees, or count. The unit for frequency can be set in Hz or RPM .

 

After the counter setup is finished, the math channel setup for traveled distance and velocity can be set. The first math channel is used to calculate the displacement. This is done with the dynamic wheel radius.

The equation for displacement reads:

 

The second math channel is used to measure the velocity of the car. The same dynamic wheel radius is used for this calculation.

The equation for velocity reads:

 

All - measured and calculated – channels are available in real time without any hardware or additional wiring. The figure below shows the measurement results from the wheel sensor.