Hands-Off Detection (HOD) – crucial for Driver Assistance and Automated Driving Systems
What is the need to check if the Driver is in Control… ?
With an increasing number of vehicles equipped with Advanced Driver Assistance Systems (ADAS) features, capable to partially control the longitudinal and lateral movement of the car, some drivers tend to show some overreliance to those assistance systems. Numerous instances of drivers misusing the systems, acting as if the vehicle would be “self-driving” (taking the hands off the steering wheel or even leaving the driver seat) have been recorded. Unfortunately, this irresponsible behavior has already led to fatal crashes.
Hands on the steering wheel is considered to be an indicator of the driver being in control of the vehicle. This is why we need a system which can precisely classify between hands on/off to ascertain whether the driver is in control of the vehicle.
How is the UN addressing system misuse …?
Regulatory authorities have taken a significant step to prevent drivers from misusing steering assistance systems that are designed for hands-on use. To address driver misuse related safety concerns, the UN Regulation 79 (R79) mandates that vehicles equipped with a Lane Keeping Assist System (LKAS) must be capable of detecting whether the driver is in control of the steering. Additionally, it describes an escalating warning strategy as shown in the figure below.
To meet this regulation, it is of utmost importance to have a reliable & robust detection system. It is equally important to avoid setting off false alarms, although the driver effectively has control of the steering system.
IEE – The pioneers of the HOD solution
IEE, from Luxembourg, has been producing a Hands-Off Detection (HOD) sensor since the end of 2013, which is integrated into the steering wheel rim to address the system misuse concerns effectively. The lead OEM customer had identified the driver overreliance risk well ahead of regulation, and IEE could deliver the appropriate technical solution. IEE’s HOD was the first capacitive steering wheel sensor on the market, and there is an increasing need for the technology. More than 1 million cars have already been equipped with IEE’s HOD sensors. Through the use of this HOD sensor, the vehicle is able to detect precisely if the driver’s hands are on the steering wheel, and if not, initiate an appropriate warning cascade. In addition to enabling compliance to vehicle regulations, the HOD sensor also supports automatic parking systems. The automatic parking works as “hands off” system, and maneuvers the car into a parking slot. However, if the driver then touches the steering wheel, this can be understood as the driver’s wish to override the system, and the automatic parking can be deactivated.
So how exactly does this HOD sensor work?
Capacitive sensing or electric field technology forms the basis of the HOD sensor. It consists of a highly flexible multi-layer sensor mat integrated into the steering wheel, with a miniaturized electronic installed in the steering wheel’s central hub. The system measures the current flowing from the sensing electrode towards vehicle ground, which is proportional to the capacitance. When the driver touches the steering wheel, the capacitance increase is detected. The electronics can reliably classify and communicate the hands on/off status under all environmental conditions.
HOD immediately detects when the hands are taken off the steering wheel and notifies the vehicle within less than half a second. As a result, with regards to the UN R79 requirements, OEMs can initiate the warning with high precision and repeatably, and select any feasible warning time within the minimum regulatory requirements. HOD also prevents false positive warnings in situations where there is no active steering input from the driver. This is a major advantage over the torque sensors, which have limitations on straight, smooth roads with little to no irregularities, especially at low speeds.
Was the driver in control of the vehicle when the collision happened?
Hands-off functions need to address liability questions too, especially when automated driving functions will become available in the future. When the automated driving conditions are met, the driver will be allowed to take the hands off the steering, but he will have to be able to take back the control when requested by the vehicle. A safe transition between automated and manual driving modes is necessary and HOD provides crucial information. This transition requires accurate supervising, as a change in liability goes with the change of vehicle control. As a result, it is essential to know exactly when the driver has given up control of the steering system to the vehicle, respectively when the driver took back manual control. A reliable HOD sensor is the one which can correctly track this transition. In the unfortunate event of a collision, the HOD signal can help to clarify the key question regarding who was in control of the car when the incident took place.
To sum up, IEE’s HOD is a robust solution to determine whether the driver has his hands on the steering wheel in any driving scenario. It has a wide array of applications which include enabling regulatory compliance for LKAS, safe transition between manual and automated driving modes, clarification of liability questions and supporting the Human Machine Interface (HMI) concepts of advanced automated driving functions.
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