Sensor layer

What the array does

Contact force changes resistance across a piezoresistive composite.

Each taxel in the array is a pressure-sensitive resistor. When force is applied, the material's electrical resistance changes. By measuring resistance at each point in a grid, the array reconstructs a spatial force map across the contact surface.

Spatial resolution depends on two parameters: electrode pitch (the spacing between measurement points) and taxel count (the number of discrete sensing elements). Higher taxel counts capture finer spatial features. Smaller pitch captures more detail per unit area.

The array responds to both normal force (pressure into the surface) and shear force (lateral force across the surface). This distinction matters for slip detection: the distribution of shear across the contact patch encodes information about impending slip before grasp failure occurs.

Readout approach

Embedded circuitry samples resistance changes and delivers a digitized stream.

The readout circuit sits close to the sensor array. Resistance measurements are multiplexed, digitized, and streamed to the data pipeline at frequencies useful for real-time control. The sampling rate is chosen to capture force transients relevant to manipulation tasks: slip onset, contact events, force profile changes during in-hand motion.

Latency from contact event to digitized output is a key parameter for closed-loop control. The target is a signal path fast enough that the control loop can react to contact events within the timeframe of the manipulation task.

Design constraints

The sensor must conform to gripper geometry and maintain signal integrity under dynamic loading.

• Flexibility. The array conforms to curved gripper surfaces. Rigid sensing elements would create contact patches disconnected from the gripper's actual grip geometry.
• Conformability. The material must maintain consistent electrical response while deforming to match surface geometry. This is a materials engineering constraint, not just a mechanical one.
• Signal integrity under dynamic loading. Manipulation tasks involve changing contact conditions: grip force adjustments, in-hand repositioning, contact with surfaces at varying angles. The sensor response must remain interpretable across these conditions.