Alps Alpine has a developed an electronic control unit (ECU)1 for hands-off detection to support autonomous driving systems by distinguishing between variations in a driver’s grip on the steering wheel. By doing so, a vehicle’s driver assistance systems can determine when to switch between autonomous driving assistance and manual driving, and to warn the driver accordingly.
The company said it already started mass production in spring 2021 and the plan is to gradually expand deployment to a range of vehicle models, and development for next-generation models is already underway.
Technological innovation is gathering speed within the automotive domains of connected cars, autonomous driving, sharing and services, and electrification. In autonomous driving, there is growing deployment of systems that enable a vehicle, under certain conditions, to automatically follow the car in front while keeping to the lane. One recently developed advanced autonomous driving system now on the market performs all driving tasks under limited scenarios, such as while traveling on an expressway or at low speeds.
Vehicles equipped with these features need to be able to detect and assess a driver’s driving status to allow safe and smooth switching between automated and manual driving. One aspect is hands-off detection, a function for determining the status of the driver’s grip on the steering wheel that interacts with other systems for assessing driving status to enable safe switching between driver-controlled and system-controlled modes. Safety features are necessary given the ongoing sophistication of autonomous driving assistance systems, and legislation is progressing. Provisions under the R79 international regulation are one example.
Determining the right time to switch between autonomous driving assistance and manual driving requires constant monitoring of the vehicle’s drive status and the driver’s driving posture to ensure safety. If the continuation of autonomous driving assistance is deemed inappropriate, the driver needs to be quickly warned that the assistance is to be disengaged and urged to immediately revert to manual driving. Safety assurances demand much more precise detection of diverse variations of the driver’s grip on the steering wheel.
Alps Alpine’s new hands-off detection ECU uses capacitive sensing for steering wheel touch detection due to its cost and functional performance. Data obtained via a special-purpose capacitive sensor, wrapped around the steering wheel, is used to determine if the driver is touching it and conveys the assessment to an advanced driver assistance system (ADAS). Whereas existing hands-off detection systems are mono-zone setups, with a single electrode, Alps Alpine has developed a multi-zone configuration with four electrodes (see diagram). Dividing the steering wheel and grip patterns into smaller sections enables efficient system switching and enhanced touch assessment reliability.
The company has used its experience in producing touch panels for notebook PCs and game consoles in the 1990s and automotive control panels for capacitive touch-type in-vehicle infotainment (IVI) systems in the 2010s. Utilizing this knowledge, it has developed the hands-off detection ECU for use with a special-purpose steering wheel capacitive sensor. Deliveries to steering wheel manufacturers began in spring 2021. The ECU takes into account the need for resilience to physical stress when employing capacitive control, and to maintain resistance to environmental factors – temperature, humidity and electromagnetic noise – and the feel of the sensor itself.
The sensor electrode in the ECU is divided into four sections to enable identification of various grip states. This allows a more detailed assessment of driving status than a basic touching/not touching determination reached using an existing single-electrode sensor. Alps Alpine has developed an original capacitive control ASIC with improved durability and versatility for conformance to strict automotive standards. Steering wheel design, sensor material, and electromagnetic compatibility conditions vary from model to model, leading to variance in data obtained via the capacitive sensor. To accommodate the separate circumstances, Alps Alpine said it can supply an originally developed algorithm that seeks individual optimization, for example with parameter changes.