Why Haptics matter
Since we were toddlers when we stood on tip-toe to turn on the lights we have become ‘trained’ in how a switch works. You feel when your finger is on the switch, to build up pressure, and on reaching the right force threshold you feel the switch move under your finger, you hear the ‘click’, and see the lights come on (it’s called ‘multi-modal sensory fusion’).
As adults we do this without thinking, but if any one of those elements jars with our senses, then our conscious thoughts are interrupted or distracted. So when user experience is good we don’t even notice it, but when it’s bad we do…in a bad way. User experience must enhance our productivity or enjoyment without getting in the way. Now we are all using touch displays on our smart phones, tablets, and increasingly on our computers, we are becoming sensitised to the lack of naturalistic user interface – we are tapping away at a ‘dead’ screen. We reach out to our tablet and it doesn’t even have the grace to give us a polite handshake.
There are two key elements to being able to deliver that naturalistic tactile response from a touch screen:
1. Understanding the parameters of a mechanical switch, key-stroke or button press that relate to the human factors that interpret the richness of the sensation.
2. Owning the technology that utilises human factors knowledge to replicate complex sensations of a mechanical switch or key that moves on a non-moving touch screen.
At Redux Labs, we believe we have both, and have built that knowledge and IP into products that we are able to demonstrate in real-world systems;
next; capture and render…
Switch/Key/Button Data Capture System, and Haptics Sensation Renderer
Redux has developed a suite of tools that allows the complex attributes of a mechanical switch to be measured and analysed. We capture up to 30 channels of data including multi-axis force, acceleration, displacement, velocity and torque. Additionally, second-order effects such as surface vibrations are measured, and also an acoustic profile – the sound of the switch clicking.
Compared with the force/displacement curves shown in mechanical switch data sheets, this defines a great deal more about what makes a switch feel like it does: why does a switch in a BMW feel different from a switch in a Ford? – for example.
Those key elements of the multidimensional data can be revealed and isolated by transforming into an appropriate domain. Flicking a switch is not just an impulse response, it is a complex interaction. There are many mechanical transfer functions that give character or ‘signature feel’ to the switch. One thing is certain – in a context such as the ‘On’ button on a smart phone, you cannot replicate [the sensation of] a mechanical switch, using a high-Q (resonant) actuator: for example, by blipping the vibro-motor in the phone. It will feel wrong, which means it brings itself to the attention of the user’s consciousness, which in turn means it ‘gets in the way’.
Redux Labs’ “bending wave haptics” allows a multi-octave waveform to be focused at the point of touch to deliver a highly realistic replication of the sensation of actuating a mechanical switch. They are delivered as deformations of a flat panel, by way of waveforms launched into the panel by edge-mounted piezo-electric drivers. The associated tools allow numerous parameters to be adjusted to create modified or even brand-new sensations.
These sensations, that are actually synthesised waveforms of frequencies detectable by the human nervous system, can be combined with captured or synthesised sound files if desired, to create the sound and feel of a mechanical switch. Alternatively, the switching action can be silent.
Once engineers have crafted the ideal haptics waveforms for the application these can be quickly evaluated on Redux’ haptics renderer. This allows a block model of the target device attached to the rendering ‘engine’ to be activated with the haptic waveforms so that the developer can get a contextual look and feel of how it will perform when haptic-enabled. Of course, surface textures, and other elements which enable a keyboard or switch pack – on a flat touch panel – to be felt as if in 3D can all be developed and evaluated at this stage. This includes background, “always-on” effects produced by the haptics waveforms – defining the “unpressed” buttons, for example – as well as those generated when the virtual button is activated. The sensations can then be committed to a unique customer library and assigned to a specific new product development.
next; design-in…
Designing-in haptics
Having established the ideal suite of haptics tactile and audio responses, they need to be designed-in to the end product. Redux Labs works with its customers through this phase to optimise aspects of the design; as well as to design aspects that are key to getting the best feel from the product. This includes measuring the mechanical properties and characteristics of the touch screen stack-up and assessing which actuator technologies are most suitable and where they should be positioned. Then we model and simulate the interaction of the touch panel with its mechanical surroundings and compute the required actuator performance to deliver the haptic sensations.
Electronic design is simple – the respective algorithms and the custom sensation library and haptic ‘maps’ require a modest amount of processing power. A simple microcontroller will do the job, or it can be embedded in a latency-managed part of a core processor. The driver circuitry for the actuators is a straightforward amplifier design. The input is simple xyz (touch location and force) cross-referenced to the haptic map that is contextual with what is displayed on the screen, with points and vectors for haptic-enabled locations.
At present, most active customers exploring the technology are automotive and aerospace brands who need to move on from old-fashioned, failure-prone, mechanical switches to touch panel switches and displays. In these cases, it is a safety essential to be able to locate and feel the switch function without visual distraction – haptics is a must-have. This evolution is rapidly being followed by the consumer electronics sector with the convergence of in-car and mobile-device user experience being driven by Graphical User Interface commonality, and it is predicted that we will see a rapidly growing demand for naturalistic haptics solutions in tablets, phones and computers.
James Lewis has had management roles in several semiconductor and electronics-industry start-ups and is currently CEO of Redux Labs, www.reduxst.com
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