Haptics that feel right – and hold up in series production.

For OEMs, suppliers at every tier and technology providers – as independent consultancy or with active involvement in the project: from specification and the selection of technology and design to validation and series launch, for passive and active haptics. reisinger engineering does not ship products of its own; it helps develop them.

Effective static characteristics describe the force–travel behaviour precisely at the features people actually feel – such as force drop, switching travel and return. Precisely specified and given perception-based, effective tolerances, they become an enforceable requirement. Vague characteristics and blanket tolerances, by contrast, create cost and pressure in the wrong places without securing tangible quality. Dynamically, they are additionally validated with IDM.

In friction-based haptics, a surface is made to vibrate ultrasonically. This changes the perceived friction under the sliding finger: textures or detents become tangible without the surface visibly moving. For series production, technical compliance (ultrasonic acoustics) and suitable measurement are as decisive as the haptics itself.

Often fewer than assumed – what matters is physically correct design. With physically grounded design – for example with an almost motionless surface instead of a lateral shaker – even large, curved displays can be given high-quality haptics with very few actuators.

Haptic specification is the technical process of defining measurable parameters that describe how a control feels – actuation force, surface texture, feedback timing, perceived resistance. It makes it possible to communicate requirements to suppliers objectively, verify the series and base quality discussions on data rather than gut feeling.

IDM is a measurement method substantially co-developed by Dr.-Ing. Jörg Reisinger that captures the vibration behaviour of a control at the real operating point of human interaction with a normalised finger impedance – enabling a close-to-perception, objective assessment. Published at EuroHaptics 2014 and detailed in “Engineering Haptic Devices” (Springer, 2023).

Passive (mechanical) controls create their sense of quality through construction and characteristic curve. Active haptics uses actuators: vibrotactile (electromagnetic, piezoelectric), friction-based (ultrasonic) and electrostatic/capacitive. Each technology has specific advantages and disadvantages in latency, force, packaging, cost and integration – the choice follows from the desired perception and the system architecture from the UI to the actuator.

Because perceived quality emerges at the end of a chain – from UI and design through framework, architecture and protocol to the actuator. This chain determines latency and its jitter, how precisely the feedback follows the input, which effects can be rendered and whether haptics, visuals and sound match. Optimising the actuator alone wastes quality; typical failures arise at the interfaces between OEM, supplier, chip and actuator provider. That is why the latency budget, the effect library and alignment with the UX belong in the specification early on.

Psychophysics describes the relationship between a physical stimulus and its perception. In haptics it connects technical quantities – force, displacement, acceleration, frequency – with what a person actually feels, such as perception thresholds and the just noticeable difference (JND). This allows specifications to focus on the parameters that are felt and tolerances to be granted where differences are imperceptible anyway.

Passive haptics refers to the tactile quality of purely mechanical controls – switches, rotary controls, buttons – that create a sense of quality through their construction. Active haptics uses actuators (piezoelectric, electromagnetic, electrostatic) for on-demand feedback, for example on touch displays without mechanical travel. Both require different specification and assessment methods.

In three steps: first, a robust, perception-based specification with measurable target values and tolerances; second, reproducible measurement for quality assurance; third, clear acceptance criteria for supplier discussions. Without this system, haptic quality stays tied to individuals – neither transferable nor scalable.