Making the HMI experience feel good with haptic technology
02 March 2020
The term haptics comes from the Greek haptikos or haptesthai – meaning of, or relating to, the sensation of touch. Little could the ancient Greeks realise how significantly the use of haptics has, and will continue to change the way humans interact with computer-based systems.
This article was originally featured in the March 2020 issue of EPDT magazine [read the digital issue]. Sign up to receive your own copy each month.
And as Richard Mount, Director of Sales & Marketing at ASIC & MEMS solutions provider, Swindon Silicon Systems tells us, these systems can now be found in many applications, including smartphones, cars, on the factory floor in machine control HMIs (human machine interfaces) or even in medical facilities, embedded in the latest medical systems used in theatres and in-patient care.
In almost every application where users need to touch a screen or operate some other kind of electronic control, haptics can play a part. Because control systems based on electronics technology continue at a pace to replace those with a traditional mechanical interface, the sensations of touching, turning, pushing and so on are being lost. Haptic technology mirrors this feedback and can enable a traditional ‘feel’ when using the latest devices.
Such tactile feedbacks can add totally new functions, as well as increase control and safety levels, while allowing designers to really differentiate their product offering. Let’s look at cars as the perfect example of haptics in use today.
Driving today: haptics at work
There are many published reports that extoll the virtues of adopting haptics technology in vehicles. All of these make much of the fact that the use of haptics not only helps to make driving the car inherently safer, but also makes for a more enjoyable and informative motoring experience. As the automotive industry moves towards truly autonomous, vehicles are being developed and launched that just require switching on, steering and switching off. They can obey speed limits, avoid cyclists and pedestrians, maintain lane discipline, as well as distance from the car in front and, when necessary, park themselves. They can also warn the driver when the car ‘thinks’ full attention is lost.
These cars can develop a clear understanding about what is happening around them and can alert the driver accordingly. Increasingly, this is no longer by warning lights and audible signals, but by a haptic sensation through the steering wheel for example. Here, the wheel will vibrate if an unexpected lane change occurs, while part of the driver’s seat will shake if the car senses a tired driver. Some models feature a touchpad controller, complete with haptic technology, that allows drivers to ‘feel’ their way around features like sat nav and the audio system.
Even the most basic car on the road today gives the driver a lot of information, although most of his/her attention must be on what’s happening outside. Experts argue that the driver’s full visual attention should remain on the road ahead and not on the increasingly complex dashboard displays and controls that are now standard features. Currently, the majority of these displays are touchscreens that give no feedback to the driver when touched apart from an audible sound. The next generation infotainment systems will include tactile responses, perhaps with visual confirmation via a head-up display.
Physical size and the type of haptic effect required by the system designer will determine the choice of actuator. Most haptic applications use a vibration effect, and the majority of these use a low-cost eccentric rotating mass (ERM) actuator. Here, a tiny unbalanced weight is fixed to the shaft of a motor attached to the device in question. When the shaft rotates, the imbalance causes the vibration.
More recent designs use what is called a linear resonant actuator (LRA), which vibrates when a tiny mass is moved up and down using a simple magnetic voice coil. In our experience, LRA-based designs have a faster response time than those using an ERM actuator.
More precise ‘local’ vibrations, with less noise and in a smaller device, are made possible by incorporating piezoelectric effect actuators. These tend to be more fragile in use, and need more power, but they enable the precise control of high definition haptics in, for example, the latest touchscreens. A key advantage of piezoelectric actuators is that they can be very thin when compared to LRA and ERM actuators, making them perfect for keyboards and many other applications that require a low-profile.
For many system designers, incorporating haptic technology presents a new challenge. As a result, device manufacturers and software developers have tried hard to make their products simple to design in to new products – or even add to a current offering.
A single chip haptic solution
In its basic form, a haptic system will include a sensor – imagine a touchpad key for example – which in turn transmits the input stimulus signal to a microcontroller. The microcontroller produces an appropriate output, which is then amplified and sent to the actuator. The actuator then generates the vibration required by the system.
By nature of their application, haptic devices need to feature a high level of integration in a tiny footprint and, although low-power consumption is preferred, but not essential, in mains-powered systems, battery-operated applications demand extremely low levels of power usage. Working with a mixed signal ASICs specialist like Swindon Silicon Systems can make the adoption of haptic technology even easier, since almost all of the functionality needed is contained in a single, tiny device.
New technology trends such as haptics require new and innovative approaches to realise the unique hardware being designed and manufactured. The optimal way to achieve this is through the use of mixed signal ASIC technology.
There may be standard ICs available for the system designer, but haptics technology warrants a tailored solution for the best possible user experience. In essence, high definition haptic technology must balance sufficient processing bandwidth with speed of response, coupled with low power to improve battery life and heat dissipation. In the automotive market especially, reliability and robustness are also extremely important aspects along with size and performance. These areas are where an optimised ASIC solution allows manufacturers to perfectly balance these trade-offs, and in so doing, deliver an enhanced HMI experience.
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