Steering Angle Sensor : Diagram, Working, Symptoms, Functions, Calibration & Its Uses

Currently, most vehicles are equipped with ESC (Electronic stability control) for overall security. ESC is a series of sensors that function with a computer to enhance vehicle strength by sensing and decreasing traction loss. In the ESC system, there are some of the most significant sensors are used like wheel speed, yaw rate, steering angle, and lateral acceleration sensor. All these ESC sensors mainly depend on each other to provide the ESC module with precise data by connecting the vehicle’s steering wheel with the wheels to control the speed of turn (or) traction control. At present, several vehicles are designed with Electric Power Steering (EPS), Advanced Driver Assistance Systems (ADAS), Variable Effort Power Steering, Lane Keep Assist (LKA), and many more depending on precise data from the steering angle sensor. This article provides brief information on a steering angle sensor or SAS, its working, and its applications.

What is a Steering Angle Sensor?

A steering angle sensor in a vehicle is a communication link between your vehicle’s computer system and steering wheel. These sensors are essential to use in modern vehicle security which helps in maintaining stability & control of a vehicle.

This sensor helps measure the position angle & speed of the turn of the steering wheel. This sensor is arranged in the vehicle’s steering column. To provide idleness & data validation, the above one-angle sensor is used. Generally, the steering control program requires two signals from two sensors to verify the position of the steering wheel. So these types of sensors are mostly based on magnetic, inductive, or optical working principles.

Steering angle sensors are available in two types: analog & digital which have similar functions, although they determine data differently. Analog sensor uses variations within voltage signals to decide the steering speed of rotation & positioning of angle. The digital sensor uses LED lights to determine the steering input angle.

Steering Angle Sensor Diagram

The steering angle sensor has a slit disc that works as a unit to rotate with the steering wheel and set of photo interrupters. This sensor is fixed to the assembly of the turn signal switch which detects the direction & angle of steering rotating.

Every photo interrupter has an LED & a photo transistor which are arranged facing each other. So it converts the change within the light irradiation between the two elements for the ON/OFF signals. In this sensor, the slit disc turns in between the phototransistor & LED pair of photo interrupters.

When the steering wheel is functioning, the slit disc turns with the wheel like a unit & shuts to make the light transmission in between the two elements. So a couple of photo interrupters contain phases & the suspension control ECU notices the steering direction & angle depending on the changes of every output. When the turning angle of the steering wheel is huge & the wheel speed is superior as compared to a fixed value, then ECU causes the damping power to rise.

Steering Angle Sensor Working Principle

The steering angle sensor works by determining the vehicle the driver desires to steer and matching the wheel steering with the wheels of the vehicle. This sensor is arranged in the steering column which is always above one sensor that is enclosed together within a single unit for accuracy, diagnostics, and redundancy.

The steering angle sensor also provides required information on how quickly the vehicle’s steering wheel is being rotated. In low-speed operation of the vehicle, a steering wheel is rotated very quickly but, it is not normal at highway speeds. If the vehicle driver is rotating the wheel at a higher speed while driving a highway then the ESC interprets that as a sign the vehicle has lost its intended way control.

Symptoms of Steering Angle Sensor

A malfunctioning of this sensor can cause many issues with the ADAS & ESC system which are discussed below.

Warning Light of ESC

The warning light of the ESC on the dashboard is frequently the primary indication of a malfunction. Whenever the system notices an error in between the steering input of the driver & actual path of the vehicle then the warning light comes on.

Conflicting Steering Reaction

This conflicting steering reaction is one more faulty indication of the sensor. So this is a very common problem after a wheel position set apart by the vehicle steering to one face (or) the feeling of is lighter or heavier than usual.

Stability Control Loss

This stability control loss feature can also mean you have a defective sensor. Some features like; electronic stability control, active steering, and traction control might end up functioning correctly.

Functions

The steering angle sensor is used to observe the situation and motion condition of the vehicle’s steering wheel. This sensor also provides significant information for different systems within the vehicle like; the adaptive cruise control system stability control system & lane departure warning system. The functions of the steering angle sensor are discussed below.

Traction Control

SAS data helps in controlling traction by helping the vehicle decide whether there is an understeer or over-steer by allowing the traction control system to create adjustments.

Stability Control

The SAS is an essential part of the electronic stability control system of the vehicle. It measures constantly & reports the position and angle of the steering wheel to the onboard computer of the vehicle.

Yaw Rate & Lateral Acceleration Sensors

The SAS data is utilized in combination with data from both yaw rate & lateral acceleration sensors to decide the actual direction & movement of the vehicle. This assists the stability control system of a vehicle to respond properly to unexpected changes within unexpected or steering road conditions.

SAS Calibration

The steering angle sensor calibration is a significant step for the working of ESC & ADAS systems. Sensor calibration simply provides precise measurements by considering real-world variables such as alignment issues, tire wear, or road curvature. If this sensor is not properly calibrated, then ADAS might misinterpret the inputs of steering which leads to unsuitable vehicle reactions or false warnings.

The calibration of SAS is the procedure of adjusting (or) resetting the sensor to make sure that it notices the steering angle precisely and gives proper and consistent information to the systems of the vehicle.

Under What Conditions is required to calibrate the Steering Angle?

We need to calibrate the vehicle’s steering angle to make sure that the wheels of the vehicle are connected properly & that the vehicle stays directly on the road. Thus, it is essential to calibrate the steering angle in some conditions include the following.

After the Alignment of the Wheel

Whenever we have carried out the alignment of the wheel on the vehicle, then it is essential to calibrate the steering angle to make sure that the vehicle path is straight.

After Replacing the SAS

If the SAS fails (or) needs to be changed, then the latest sensor has to be calibrated to make sure that it provides precise data for the stability control system of the vehicle.

After Steering Components Replacement (or) Suspension

If any delay or steering components like ball joints, tie rods, and control arms have been changed, the SAS needs to be calibrated to make sure the wheels are still aligned properly.

After a Collision

If the vehicle has a crash, it is essential to calibrate the vehicle’s steering angle to make sure that the vehicle can drive straight.

Thus, SAS calibration may be necessary when there is a change in wheel alignment or steering component. Certainly, throughout the calibration procedure, the makers must follow calibration recommendations to make sure that they execute the standard properly.

How to Calibrate SAS?

The process of calibrating the SAS changes simply based on the model and brand of the vehicle. Here is a general guide on the calibration process of a steering angle sensor.

Connect the Scanner Tool to the Car

First, need to connect the scanner to the port OBD-II of the vehicle, and choose the suitable function for calibrating the SAS.

Place the Steering Wheel of the Vehicle

Confirm the steering wheel of the vehicle is centered & the wheels are pointing straight in front. Follow the prompts on the scan tool to create the calibration procedure. Some vehicles may require rotating the steering wheel in a certain way or traveling within a straight line at a certain speed.

Completion Procedure

After the calibration process is finished, the scanning tool will prompt whether the calibration of the sensor is successful. If the sensor is successful, then you can separate the scan tool & test drive the vehicle to confirm the steering is working correctly.

Thus, there are different calibration tools for this sensor like automotive scan tools, wheel alignment equipment, turntable wheel chocks, torque wrench, iSmartLink D01, and iSmartIMMO 801.

Characteristics

The characteristics of the steering angle sensor include the following.

• The steering-angle sensor or SAS is based on Giant Magnetoresistance technology & it provides a complete steering-angle value above the complete steering-angle range.
• The output of this sensor’s exact angle in the measurement range openly after ignition-on.
• The steering wheel movement is not necessary even after detachment & reinstallation of the power supply.
• It doesn’t need a standby current.
• The steering angle as well as steering-angle velocity is made accessible through the CAN interface.
• In safety systems, these sensor-internal possibility tests & also special self-diagnostic functions permit the utilization of this sensor.
• This sensor also allows the incorporation of a second microprocessor mainly for security-related applications.

How to Reset Steering Angle Sensor without Scanner?

To reset the SAS without a scanner, then you have to execute a self-calibration process. This process changes based on the model of your vehicle, although it normally involves the following steps:

• Discover a level face to park your vehicle on.
• Turn ON the ignition position, however, do not begin the engine.
• Turn the steering wheel completely to the left & after that completely to the right.
• Repeat the above third step three times.
• Turn OFF the ignition position.
• So this process must reset the SAS. If you have any issues still then you may require to take your vehicle to a capable mechanic for further repair or diagnosis.

Steering Angle Sensor Role in Vehicle Security

Steering angle sensors are essential in modern vehicle security because they help in maintaining vehicle stability & control.

ESC (Electronic Stability Control)

These systems utilize data from the SAS for detecting whenever you lose steering control of the vehicle. These sensors apply brakes automatically to assist in “steering” the vehicle within the way you desire to go.
By maintaining an eye on the vehicle’s steering angle and evaluating it to the actual lane, electronic stability control can spot conditions wherever your intended lane doesn’t match the actual one.

So this occurs during unexpected moves (or) on slippery surfaces. Whenever this occurs, electronic stability control steps in by applying the vehicle brakes to particular wheels. This assists in the regained stability of the vehicle & decreases the skidding chances (or) spinning beyond control.

Advanced Driver Assistance Systems

ADAS technologies use steering angle sensors to monitor the intended steering inputs of the driver & contrast them to the actual vehicle’s movement. For instance, if the vehicle begins drifting from its path without utilizing the turn signal, then the lane-keeping assist system uses the steering angle information to discover what is required to be done, quietly pushing the backside of the vehicle into the correct lane.

In addition, if the data of this sensor indicates that the vehicle driver is steering in the direction of a detected vehicle in the blind spot, then the system alerts the vehicle driver. So this can be attained through visual cues like; flashing lights within the side-view mirror (or) audible alerts.

Autonomous Driving

Steering angle sensors are very significant in the future for the combination of autonomous driving. When self-driving cars attempt to navigate roads securely without personal intrusion, they depend on precise & constant steering angle data. With the help of sensor data, self-driving cars can check they plan exactly, reside in the path & navigate constantly. So this helps in creating a safer & very efficient transportation system.

Applications/Uses

The steering angle sensor applications or uses include the following.

• The steering angle sensor or SAR simply measures the position angle & rate of turn of the steering wheel.
• This sensor decides wherever the driver desires to steer to match the steering wheel with the wheels of the vehicle.
• This is a significant part of the safety system of a vehicle which sends the steering wheel’s turning speed, angle of the wheel & other significant data to the computer system of a particular vehicle.
• It is used to monitor steering input by simply detecting the position & rate of rotation of the steering wheel.
• This sensor helps in providing data to the car regarding the condition of the steering wheel.
• The steering angle sensor is utilized by various ADAS functions which range from blind-spot detection to autonomous driving.
• This sensor is the most significant part of the ECS of the car.

Thus, this is an overview of steering angle sensors, their working, and their applications. This sensor simply measures the position angle & speed of the turn of the steering wheel in a car. This sensor is arranged in the steering line of the vehicle. Above one angle sensor can be utilized for providing data validation & redundancy. Here is a question for you, what are the different sensors used in automobiles?