Motor type bounds the achievable haptic vocabulary

What it is

Motor type sets how many haptic patterns you can design. Hardware is not a neutral renderer: it fixes the shortest pulse, the smallest gap, the controllable dimensions, and the frequency range. The set of patterns a designer can express is the intersection of those constraints, not an arbitrary list of desired textures.

Why it happens

Vocabulary size follows from the number of controllable dimensions. An ERM offers mostly amplitude, with frequency coupled to speed, so patterns reduce to combinations of duration and repetition; an LRA resolves time finely enough to separate pulses, but tunes frequency only narrowly. With one adjustable dimension, patterns crowd together perceptually and the vocabulary stays small. Cross-device differences drop the same pattern table into different subsets, opening a gap between design intent and what users actually feel.

Studying it

Start by extracting hardware capability—minimum pulse width, minimum gap, controllable dimensions, efficiency curve—then validate the usable vocabulary with identification experiments, tracking confusion matrices and accuracy as pattern count grows. Cross-device studies compare the same pattern table across models to quantify how intent degrades. Report the exact models and drive scheme, since parameters do not extrapolate.

Where it stops holding

Hardware is not the only bound: the number of patterns users reliably separate is usually below what the actuator can generate, so perception caps the vocabulary as well. When a product targets a single model, cross-device degradation is moot. With external accessories, capability is typically below the built-in motor, and the vocabulary must be defined on the smaller intersection.

Applying it

• Obtain the actuator capability list for target models before defining the pattern table, rather than designing patterns and hunting for hardware.
• Split the table into "every target model can render this" and "premium-only," with a stated fallback for degradation.
• Keep the total pattern count below what hardware and perception jointly allow.
• Verification: run identification tests on every target model, log accuracy and confusions per pattern, and provide degraded substitutes for any pattern below threshold.

Related

• Within the group: D3.01.1 Eccentric rotating mass motors start and stop slowly, so short pulses are hard · D3.01.2 Linear resonant actuators start and stop fast, giving a crisp tap
• Adjacent: D3.10 Discriminable size of the haptic vocabulary · D3.14 Cross-device differences in haptic capability
• Search terms: haptic vocabulary · actuator capability · device fragmentation