Yaw Rate Sensor : Circuit, Types, Differences, Symptoms, Testing & Its Applications

Generally, a vehicle experiences tilt or body roll whenever it’s breaking, accelerating, or moving around corners. But, there is a point where extreme yaw or tilt causes your car to lose its grip. Thus, modern vehicles are designed with yaw rate sensors for executing corrective actions. This sensor simply measures how fast & how much a vehicle is tilting with tuning forks or gyroscopes. If this sensor properly functions, then it keeps the vehicle stable. If this sensor is not working properly then you will observe some symptoms like stability, an illuminated check engine light (or) traction control lights. This article briefly explains a yaw rate sensor, its working, types, and applications.

What is a Yaw Rate Sensor?

A type of automobile sensor that uses tuning forks or gyroscopes to measure how fast and how much a vehicle is tilting is known as a yaw rate sensor. This is a significant component within an electronic stability control or stability control system of the vehicle. The yaw rate sensor function is to provide motorists with improved security & control in the most hard driving conditions.

This sensor is installed frequently in the middle of the vehicle which includes a two-sided tuning fork internally that is activated through a high frequency to enhance the apparent fork mass. The downside of the fork is connected to the vehicle so that it rotates together by the chassis.

Naturally, the upper fork responds more slowly due to its large mass, thus it does not alter its direction very quickly. This makes the sensor’s inner region of the tuning fork twist. The amount of twisting can be measured to give a worth for the yaw rate. So this action gives the controller the number of degrees for each unit of time that the vehicle turns around its axis.

Yaw Rate Sensor Working Principle

A Yaw Rate Sensor works by measuring the angular velocity of a vehicle regarding its vertical axis in radians per second or degrees to decide the direction of the vehicle when it hard-corners (or) threatens to overturn.

By contrasting the actual yaw rate of the vehicle to the target yaw rate, the onboard computer identifies to what level the vehicle may be over or under steering and what remedial action is required. The remedial actions are; decreasing engine power & applying the vehicle brake on a single or number of wheels of the vehicle to realign.

Yaw Rate Sensor Circuit

The yaw rate sensor & G sensor with ESC are shown below. Whenever the vehicle is rotating about a vertical axis then this sensor notices the yaw rate automatically through the vibration change of the plate fork in the sensor. If the velocity of the yaw achieves the specific velocity once it notices the yawing of the vehicle, then ESC control can be reactivated.

The G sensor (Lateral or Longitudinal) detects the lateral gravity of the vehicle. A tiny element within the sensor is connected to a deflectable lever arm through later G. Lateral G magnitude & direction can be loaded to a vehicle which is called electrostatic capacity modifying based on lateral G.

The longitudinal G sensor is installed within the yaw-rate sensor which detects the vertical acceleration of the car whereas the lateral G sensor senses lateral acceleration of the car. So, the HECU utilizes these signals mainly for the function of Hill Start Assist Control.

Types of Yaw Rate Sensor

There are two kinds of yaw-rate sensors like; piezoelectric & micromechanical which are discussed below.

Piezoelectric Yaw Rate Sensor

The piezoelectric yaw rate sensor has a tuning fork-shaped structure including four piezoelectric elements where two elements are on top & remaining two are below. The upper elements generate no voltage whenever the slip angle is zero because no Coriolis force operates on them. However, when cornering, the rotating movement can cause the upper portion of the tuning fork to go away from the oscillatory plane and create an alternating voltage which is proportional to the oscillatory speed & yaw rate. The sign of the output signal mainly depends on the path of rotation.

Micromechanical Yaw Rate Sensor

This sensor includes a first yaw-rate sensor element which provides a first sensor signal. This signal has data regarding a rotation approximately a first rotating axis. The second yaw-rate sensor element of this sensor provides a second sensor signal that has data regarding a revolution around a second rotational axis. This axis is perpendicular to the primary rotational axis and a drive. A drive drives the primary yaw-rate sensor element & a coupling link to couple these two sensor elements mechanically to one another. Thus, driving the first yaw-rate sensor element causes the driving of the second yaw-rate sensor element.

Yaw Rate Sensor Vs Steering Angle Sensor

The difference between the yaw rate sensor and the steering angle sensor includes the following.

Bad Symptoms

If this sensor properly works, it helps in keeping your vehicle constant. In some cases, it will save your life from an accident by losing vehicle control. But similar to any other type of automobile sensor, this sensor can also develop some problems. So if your sensor doesn’t work, it might show some symptoms like the following.

Check Engine Light will Illuminate

Whenever the yaw rate sensor is working properly then information regarding the yaw rate can be transmitted to the computer of the vehicle. But, if it is not noticing signals from the sensor, the light of your check engine will illuminate to update you regarding an issue.

A check engine light activates due to a wide variety of problems, thus there might be more fundamental problems than just a difficulty with the sensor. To ensure that, there are any other problems present within your vehicle, you must utilize a scan tool.

Traction Control Lights/Illuminated Stability

The stability & traction control system of a vehicle requires data from the sensor to function correctly. If there is a trouble with the sensor then any one of these lights can turn on on your dashboard. So the stability & traction control lights only illuminate normally when they are disabled by the driver. If you see either of these lights illuminate, you should go to a mechanic immediately to diagnose the issue. You shouldn’t drive with this problem because it is a key safety issue. So an illuminated stability & traction control light can indicate a bad yaw rate sensor.

Intermittently Flashes of the Stability Control Light

The stability control light blinks ON & OFF whenever there is an issue with the sensor. However, this can be caused by other defective components. Once this light blinks then first you must stop & restart your car. If the indicator flashes continue then need to consult a mechanic if possible.

This sensor is a significant component in your stability & traction control systems because these systems might not work. Generally, driving a vehicle without this sensor is very risky. So you must go to a mechanic once you observe any of these signs in your vehicle

Stability Control Loss

Whenever the sensor working fails, then it can lead to the stability control systems loss within the vehicle. So these systems depend on precise data about the rotating movement of the vehicle given by the sensor. If this sensor is not working properly, the stability control systems cannot effectively interfere with the proposed path.

As a result, the vehicle will become more vulnerable to sliding or skidding during sudden maneuvers or turns. These systems cannot work optimally without the right input from the sensor. So this increases the chance of accidents (or) loss of control during challenging driving conditions.

Impaired Traction Control

These sensors are incorporated closely with traction control systems to optimize traction & avoid wheel slip. Once this sensor working fails, the traction control system may not get precise data about the rotational motion vehicle. As a result, it may be not capable of applying the required brake force to wheels which leads to reduced traction & compromising the ability of the vehicle to maintain a grip above slippery surfaces.

Increased Risk of Rollover

These sensors are very important in rollover prevention systems which use the sensor’s data for noticing excessive body roll and to adjust brake power on individual wheels to counteract it. In the lack of consistent yaw data, the rollover prevention systems of vehicles may fall short of noticing and lessening the risk of rollover potentially placing the security of occupants at risk.

Functionality of Altered Abs

The ABS mainly depends on the data of the yaw rate sensor to decide if any vehicle is at risk of skidding in braking. But by adjusting brake force on individual wheels, the anti-lock braking system will ensure that the vehicle wheels keep traction during braking. So a bad yaw rate sensor can impair the ability of ABS to precisely detect wheel slip & apply the suitable brake force, which leads to compromised braking act & longer stopping distances.

Onboard Diagnostics Fault Codes

A malfunctioning sensor generates OBD2 fault codes within the onboard diagnostics system of the vehicle. So these fault codes can be accessed & read with a reader or an OBD car scanner. It allows you to ensure any problems within your diagnostics system of the car.

Whenever working of this sensor fails then it can have very severe implications for the stability & traction control of a vehicle. If you guess a yaw sensor malfunctions a capable automotive technician should check & repair it on time to ensure sure best safety & performance of the vehicle on the road.

How to Test Yaw Rate Sensor?

The yaw rate sensor can be inspected by using a hand−held tester to check its output value.

• First need to take away the two bolts & yaw rate sensor through the connector still connected.
• After that, need to connect the hand−held tester to the DLC3.
• Turn ON the ignition switch & push ON the main switch of the hand−held tester.
• Choose the DATALIST mode above the hand−held tester.
• Make sure that the sensor’s yaw rate value displayed on the hand−held tester is varying: Situate the sensor vertically to the GND & turn the sensor rotated on its center.

Applications

The applications of a yaw rate sensor include the following.

• Yaw rate sensor is used in aircraft & also ESCs in cars.
• This sensor helps in measuring the angular velocity of a vehicle about its vertical axis within degrees (or) radians for each second to decide the vehicle’s direction.
• This sensor is used in automotive applications.
• This sensor is mainly designed for high performance & mass production applications such as the VDCS (vehicle dynamic control system).
• This sensor measures the physical effects of lateral, yawing & longitudinal acceleration within vehicle control-based applications
• These sensors are significant components in various automotive applications like; rollover detection, advanced driver assistance systems & stability control systems.

Thus, this is an overview of the yaw rate sensor, working, types, and its applications. This kind of automobile sensor is useful in determining whether the vehicle is developing an inclination to turn around the vertical axis. This sensor assists the ESP control unit in deciding the current driving dynamic condition of the vehicle. So it should be located near the car’s center of gravity. Here is a question for you, what is ECU?