How ASICs can optimise haptics in the automotive space

4 mins read

“Touch comes before sight, before speech. It is the first language,” wrote poet and novelist Margaret Atwood.

We’ve long interacted with electronic devices using sound and visuals, but what about touch? In the automotive industry, haptic technology is being used as a method of quickly and safely conveying information between car and driver.

Haptics may have been implemented as early as the WW2 era. During the war, haptic feedback systems were implemented into aeroplane controls, making the control stick vibrate when the plane was beginning or likely to stall. These vibrations warned pilots and could prompt them into action, ensuring they corrected their flight path to avoid danger.

Decades later, haptic feedback became best recognised in another sector - the gaming industry. Many controllers began implementing haptic technology to add an extra layer of immersion to videogames and continue to do so today. Vibrating controllers at specific moments within games adds another layer of suspense or drama to make the game feel more real, using an additional one of the five senses.

And as the automotive sector becomes increasingly digitalised with electric vehicles and a whole host of advanced on-car sensor systems, it’s next on the list to fully unlock the benefits of haptic technology.

Overcoming the difficulties of driving

It’s no secret that driving takes a lot of concentration. The sheer amount of auditory and visual information that we must continuously process as we drive can make the experience somewhat overwhelming. As a result, our eyes and attention can become diverted, impacting reaction times and overall perceptiveness.

But haptics offer a new method of communication between driver and vehicle. Rather than being yet another light on the dashboard, or panic-inducing sounding alarm, communicating through touch can effectively cut through the noise. For example, a car with haptic feedback technology might vibrate its steering wheel to warn you to brake if it thinks you’re getting too close to the vehicle in front. And a sensor that registers your vehicle drifting away from its lane can shake your seat if it thinks your attention is dwindling.

The addition of haptic feedback also means that communication becomes two-way. Early in-car infotainment systems often provided little to no feedback. If you pressed the touchscreen, you might not know whether the input had been registered or not. This could create more of a distraction, with the driver’s attention shifting away from the road and onto the screen to check. By offering some kind of tactile response, such as a vibration when you press the ‘button’, the driver knows that the vehicle has recognised their input and can keep their focus where it matters.

Exploring haptic feedback

So, how does haptic feedback work? A basic haptic feedback system is typically comprised of three components: sensor, control system, and actuator. Sensors detect the stimulus, such as a finger on a touchscreen. This input signal is digitised by an analogue-to-digital converter (ADC) and sent to a microcontroller. The microcontroller determines the frequency and amplitude required to generate the desired vibration effect and uses this information to control the actuators.

The actuators themselves generate the vibrations, with three actuator types to choose from. Eccentric rotating mass or ERM actuators were the traditional motor of choice. These motors spin an unbalanced mass to create an uneven centripetal force, which results in forward and backward movement as well as vibrations. Where cost is the major factor and resolution is not of huge importance, ERMs are still used in simple circuits.

More common nowadays is the linear resonant actuator, or LRA. These actuators use electrical currents and magnetic fields to move a mass up and down along a single axis, generating a vibration. Because these actuators don’t rely on inertia, LRAs have a much quicker response time than ERMs, making them ideal for automotive applications when reactions must be as fast as possible.

Applications that require a low profile or a more compact actuator system might opt for piezoelectric effect actuators. These can operate at a wider range of frequencies and amplitudes compared to ERM and LRA actuators, allowing for a more precise vibration, ideal for touchscreens. They tend to have a higher power consumption, but can offer response times as quick as 1ms, compared to 40ms for ERMs and 20ms for LRAs.

Keeping control

When it comes to the control chip, the nature of these applications means that haptic devices must retain a tiny footprint. And while low power consumption isn’t essential in mains powered systems, for anything battery-operated, the system must be optimised for the lowest power usage possible.

Initial prototypes of haptic devices may be achieved using a variety of off-the-shelf ICs, but for a complete solution, opting for a tailored design offers the best possible user experience. 

This can be achieved with an Application Specific Integrated Circuit, or ASIC. ASICs are designed exactly to fit a customer’s specific requirements, resulting in a fully optimised chip. By removing unnecessary features and investing in areas relevant to the chip’s application, ASICs can offer a much lower power consumption while maintaining high performance. This also results in a lower manufacturing cost per board, with a lower bill of materials and a smaller silicon area.

Custom ASIC design also means that companies can retain their IP. ASICs are extremely difficult to reverse engineer or re-use in other designs, making them valuable in setting your product and company apart from the competition. Non-obsolescence is another advantage that comes with the use of ASICs over standard ICs. ASIC suppliers will have non-obsolescence plans ready to ensure a continuous supply of chips for the lifetime of the product.

When it comes to automotive applications, the chip must be reliable if it is to improve the driving experience and safety. Design teams will integrate as much of the circuitry as possible into an ASIC, reducing the overall component count and therefore potential points of failure.

As our cars become increasingly connected, making more use of current and emerging technologies, haptic feedback implementation is only going to grow. As we seek to optimise every aspect of the driving experience, it’s only right to take that approach right down to the component level if we want to build cars for the future.

Author details: Richard Mount is Director of Sales at ASIC design and supply company Swindon Silicon Systems