Haptic Feedback in Automotive Human Machine Interface: Reshaping Interaction and Safety

1.Introduction
2.The Key Value of Haptic Feedback within Automotive HMI
3.Key Application Scenarios
4.Technical implementation: Piezoelectric Actuators
5.Future Trends
6.Conclusion

Introduction
Today, electric vehicles are becoming larger and screening and physical button controls are less. This is the current trend. Almost every major car brand is working towards a clean and minimalist cockpit. The center console used to be studded with dozens of buttons, knobs and switches. Now it has one large touch screen.
This looks awesome but it poses a genuine problem for drivers. When it comes to driving, your eyes need to be on the road. With physical buttons, there's no need to look to find the correct control for your fingers. You press a knob, you feel a click and you know the action worked. This is known as blind operation. It is a basic safety feature.
Touchscreens negate this ability. You have to look at the screen to get the right button. Then you press it. Then you check see if it registered. This has your eyes off the road for several seconds. Studies have found that even a glance away from the road lasting just two seconds can greatly increase the risk of getting in an accident.
This is where haptic feedback comes into play. Haptic feedback refers to the fact that the device should vibrate or push back, when you touch it. This provides information to your fingers without needing your eyes. You touch the screen, the vibration catches this and you know that the action worked. So your eyes can stay on the road.
Haptic feedback is not a new technology. We've seen it used for years in smartphones. But when you apply it correctly to Automotive HMI, some performance standards are required. The response must be fast. The vibration pattern needs to be meaningful. The hardware needs to work in extremes of temperature. The automotive applications require far more engineering than consumer electronics.

The Key Value of Haptic Feedback within Automotive HMI
Every time a driver takes their eyes off the road there is danger. Haptic feedback decreases the need to look. When the volume is touched on the infotainment screen, a driver is alerted with a short vibration that indicates the press. The driver doesn't have to look at the screen to confirm the action. This keeps eyes on the road. This reduces cognitive load and saves lives.
Beyond safety, haptic feedback is a source of brand value. Two cars can have the same hardware. But if one car's touchscreen gives you a crisp, satisfying click as you press a button, and the other gives you a dull, generic buzz, well, they feel completely different. Car manufacturer spend great time thinking about how a door closes, how a button clicks, how a steering wheel feels. Haptic feedback is the next layer on that experience. The frequency of that vibration, the duration of it, the intensity, all of these can be fine, tuned to match a brand's identity. A luxury car should feel different than a sporty hatchback, despite the use of identical screen hardware.
Haptic feedback is another way to provide direct communication of vehicle status. A lane departure warning doesn't have to make a loud sound the disturbs all passengers. Instead, the steering wheel can vibrate in a particular pattern, which is felt only by the driver. This is a private, individual signal. The message reaches the right person, when it is time for it to be heard without making noise.

Key Application Scenarios
1. Infotainment Screens
The most common use case is the center touchscreen. Drivers are using it to control their navigation, music, climate and phone functions. Each of these interactions has the benefit of haptic feedback confirmation.
When a driver changes the temperature by moving a slider on the screen there is a series of short pulses that mimic what it's like to spin a physical dial. Each pulse is for one degree of change. The driver feels the adjustment going on without looking towards the screen. When the driver selects a menu item, a single crisp pulse confirms selection of the item. This is replacing the mechanical click of a physical button.
The end result is that there is less anxiety about mis-taps. When you click a physical button, you know you've done it because you hear and feel the click. Without haptic feedback, touchscreen users will often press twice because they're not sure if the first press registered. Haptic feedback brings that doubt to a close.
2. Active Safety Alerts
Today, vehicles have plenty of driver aid systems. Lane Departure Warning sees if a car drifts across lane markings. Blind Spot Detection detects vehicles that are located in the driver's blind zone. Front collision warning to detect an obstacle in the front.
These systems must be able to tell the driver right away. Audio alerts are helpful, but can startle passengers, or be drowned out by loud music. Visual alerts require the driver to look at a warning light. Haptic alerts are different. A steering wheel vibration goes immediately and directly to the driver. It cannot be missed. It does not require the driver to either look or listen. It is the most direct channel of communication available.
Different alert patterns can be used to communicate different situations. A slow pulse could indicate that a vehicle is in the blind spot. A quick strides could indicate that the car is losing its way out of the lane. Drivers learn these patterns quickly on. Over time, the vibrations become instinctive responses such as how an experienced driver reacts to the feel of the road through the steering wheel.
3. Smart Surfaces and Secrets Controls
Some vehicle designers desire that there be no visible buttons, no switches and no knobs. All nice smooth surfaces. This is possible with capacitive touch panels that are concealed under fabric, leather or wood trim. The panel is used to detect finger contact. A haptic actuator beneath the surface gives the haptic feedback.
Interior designers will get maximum flexibility in this way. Using a door panel, there may be no visible controls and the panel may still be a complete control surface. When not in use, it has the appearance of premium interior trim. When the driver wants to lower the window, they touch the smooth window surface, feel a confirmation vibration and the window moves down.
This technology is already being seen in conceptual cars and luxurious production vehicles. It will be increasingly common as trends in interior design continue to move towards clean surfaces.
4. X-by-Wire and Virtual Feedback
Traditional cars have mechanical links between the car and the driver. The steering wheel is physically connected by a shaft to the front wheels. The brake pedal is connected via hydraulic lines to the brakes. The driver senses road conditions by means of these connections.
Today's vehicles are replacing these mechanical links with electronic signals. Steer-by-wire is when the steering wheel is used to send a signal which is read by a computer and rotates the wheels via motors. There is no physical shaft. Brake-by-wire works the same way.
These systems are more precise and provide more design flexibility. But they eliminate the natural feedback that drivers use to know what's going on in the road. A good driver has the ability to feel when the wheels are about to lose grip, when brakes are reaching their limit, when the road surface changes. Without mechanical feedback such information is lost.
Haptic actuators artificially restore this information. The system reads data from sensors regarding information about the road and the grip and braking forces of the tyres. It converts this data into vibration patterns which is sent through the steering wheel or brake pedal. The driver has a sensual feeling of what is known by the system. This is a form of engineering where the lost physical information is replaced by physical signals, which is haptic signals that are precisely designed to it.

Technical implementation: Piezoelectric Actuators
Piezoelectric actuators show great advantages for car applications. Response time is faster than one millisecond. This makes the vibration seem instantaneous, and directly connected to the touch action. Power consumption is low because piezo material is capacitive in nature. They need energy to change state but they don't need much energy to hold a position. This is a concern in electric vehicles where every watt matters.
Piezoelectric actuators are thin in size. They can be mounted directly below a glass panel or below a surface of a thickness of a few millimeters. They create clean and accurate vibrations over a large frequency range. A single actuator can produce a lot of really hard clacking sound, a smooth pulsy sound, a complicated texture pattern depending on what waveform you're applying to it.
Bestarsensor is a professional supplier which focuses on high-performance piezoelectric components for demanding applications. Their components have been developed to meet automotive-grade standards, resistance to vibration and shock from use in a car and long operational life under conditions of continuous operation. For vehicle manufacturers who are implementing haptic interfaces, the reliable actuator hardware to achieve this kind of specification is a needed foundation.

Future Trends
High Definition Haptic Feedback
Current haptic feedback in vehicles is largely in the form of binary. Either, the actuator fires or it does not. The vibration sends a message of "confirmed" or "alert."
The new generation will simulate texture. Instead of a general buzz, the surface will feel different materials under your finger. Scrolling through a menu will feel like making a finger run along a rough surface. Changing a slider will feel smooth in the middle and have some resistance on the end-points. Touching various zones of the interface will have a particular feel from one another.
For this, high precision control over vibration waveforms and high-resolution actuators, which can repeat challenging patterns are required. The technology is available today in the research environment. It will be in production cars within the next couple of years.
AI-Driven Adaptive Haptic Feedback
Fixed haptic pattern works in ideal conditions. Real driving conditions aren't ideal. When you are driving on a rough gravel road you are already vibrating your whole vehicle. A haptic alert should be more powerful and to be noticeable. At highway speed, attention is more on the part of the driver and lighter feedback may be in order. In a situation of emergency braking, the haptic feedback intensity should increase automatically.
AI systems are able to monitor the driving context continuously. Road surface quality is provided by suspension data. Vehicle speed is known. Driver attention level can be estimated based on the steering inputs and eye tracking cameras. The haptic feedback system can use all of this data for dynamically by adjusting the intensity and pattern of feedback.
This makes haptic feedback more intelligent. The system becomes a better communicator because it changes according to the situation.
Multi-modal Fusion
The most effective communication uses more than one channel at a time. When a navigation system wants to inform the driver of a turn ahead, the system can use a visual arrow on screen, an audible chime and a haptic pulse through the steering wheel simultaneously. The three signals positively reinforce each other. The ways in which the driver receives the message are three independent ways.
This multimodal approach will be the norm in future design of vehicle HMI. Each modality has a designed purpose of carrying particular information. Visual signals show details. Audio signals contain level of urgency. Haptic signals are used to verify inputs from the control and provide private direction information. Together they make up a communication system which is much more capable than a single channel alone.

Conclusion
The transition to touchscreen-based vehicle controls cut out something drivers have been used to in their decades driving cars, the physical confirmation of pushing on a button and the sensation of that button clicking. This was not a small thing. It was an integral component of how the drivers kept their cars safe.
Haptic feedback technology is one that gets this connection back. It recreates the loop between what the driver's hand does and what the vehicle will go. It does this without having to add physical buttons back on to the dashboard. It works the touchscreen itself, the steering wheel, through the seat, anywhere where there is driver input.
The benefits are clear. Safety is enhanced if drivers keep their eyes on the road. User experience becomes better when the feeling of interaction is confident and precise. Brand value improves when the vehicle has the feel of having been engineered to a better degree.
Bestarsensor with its focus on piezoelectric actuator technology which offers the hardware basis to make this possible at automotive quality levels. As the standard of haptic feedback shifts from a simple confirmation pulse to high definition texture simulation to adaptive systems purposely applied by an AI, the performance requirements placed on the underlying actuator hardware will only rise. The hardware gets you started with this capability.
The intelligent cockpit of the future will communicate via sight, sound and touch all together. The physical layer of that communications relies on elements that were manufactured with the intention of performing correctly, accurately and throughout the life of the vehicle.