Throttle By Wire

Throttle by wire is one of the technologies that have been widely accepted in the automotive industry. With increasing complexity, inefficiency and wear and tear of mechanical components causing headaches with regard to reliability, automakers have begun turning to electromechanical, or even completely electronic components to replace some of the integral systems in the conventional vehicle, including throttle control, steering, shift and brakes.  

In this article, we focus on “throttle by wire” technology. It is one of the safer designs to implement as compared to an electronically-controlled steering or braking system. Often known as electronic throttle control (ETC), this system replaces the mechanical connection between the throttle pedal and the throttle valve of the engine. Instead, there are two sensors along with a control unit.  

Source: https://www.researchgate.net/figure/Schematic-of-the-electronic-throttle-control-system_fig1_262938429

Electronic Throttle Control Architecture: 

The first sensor used is the throttle pedal position sensor, which measures the extent to which the driver has pressed the pedal. This could be a pressure sensor or a resistive position sensor. Typically, pressure sensors are preferred over resistive position sensors, as the latter is noisier. This data is communicated to the electronic control unit, which determines the amount of fuel/current required, and in turn, sends this data to the ETC. The control unit then governs the extent to which the throttle valve should be opened in order to meet the acceleration demanded by the driver. There is another sensor that measures the throttle opening and sends the feedback to the controller, verifying that the commands sent to the throttle valve are accurate. The pinion gear, intermediate gear and sector gear are responsible for the reduction from the motor actuation angle to the throttle opening angle. Normally, this controller is integrated within the ECU. CAN bus is the typical communication protocol used.

Advantages over mechanical control: 

An electronic throttle controller can be integrated with a number of safety features to provide better ride dynamics. In a mechanical system, the throttle relies only on driver input to decide how far to open or close. With an electronic throttle control system, the main control unit not only reads input from the driver’s foot on the accelerator but also examines input from wheels that are slipping, wheels that have grip, the steering system and the brakes, helping correct driver error and keep the car under control. 

The biggest advantage of using electronically-controlled systems over mechanical controls is the ease of integration with other systems. ETC is no different. Having electronic control over the throttle enables automakers to easily incorporate systems such as engine control, traction control, electronic stability control and cruise control into the vehicle.  

Components of Throttle Body | Source: https://www.spectrapremium.com/en/aftermarket/north-america/electronic-throttle-body

Important Failsafes in Electronic Throttle Controller

The electronic throttle control system also has a number of fail-safes that make it an extremely reliable and fool-proof system to implement in any vehicle. In most cases, the first sign of a problem with electronic signals between the different components causes the throttle to close and keeps the engine/motor in its current state. This is of utmost importance, as any case of unintended acceleration, which can cause fatal accidents, needs to be avoided. Furthermore, there are a lot of redundancies in the sensor setup, with one or more backup sensors for each position, thus ensuring that any malfunctioning sensor does not harm the safe working of the vehicle. There is also a risk of mobile phone signals interfering with electronic control systems and communication systems. This interference needs to be prevented by properly isolating the spectrum of signal frequencies for different functions.

An ETC system can also improve vehicle safety by implementing a brake-throttle override, which can be calibrated according to the driving mode. For example, in the case of normal driving on an asphalt road, brake command will get prioritized over throttle command in case both are actuated simultaneously. However, special modes such as drift mode and drag mode have specific requirements from the brake and throttle commands. For drift mode, both commands can be equally prioritized, while for drag mode, the throttle command gets priority. This is especially important when there is unintended acceleration, and the driver presses down on the brakes. Having electronic communication between mechanical components is always easier to deal with for implementing an override protocol.  

Thus, an electronic throttle controller improves efficiency by ensuring robust and fast control. The throttle position sensor is essential for closed-loop control, while a number of fail-safes ensure higher reliability. Many OEMs have already implemented this system in their vehicles, while there is extensive research being conducted on how to improve the performance of electronic throttle control in terms of safety as well as response.  

Throttle-by-Wire Controls Development at Dorle Controls

At Dorle Controls, we focus on developing the control logic by using a hardware setup consisting of a throttle pedal, a control module, and sensors to detect the throttle opening as well as pedal position. Feedback and feedforward control is used in tandem to mitigate the errors and obtain an output as accurate as possible. For more information about X-by-wire controls development, integration, or testing, write to jpeter@dorleco.com

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