Touch pad with force sensors and actuator feedback
Electronic devices may use touch pads that have touch sensor arrays, force sensors, and actuators for providing tactile feedback. A touch pad may be mounted in a computer housing. The touch pad may have a rectangular planar touch pad member that has a glass layer covered with ink and contains a capacitive touch sensor array. Force sensors may be mounted under each of the four corners of the rectangular planar touch pad member. The force sensors may be used to measure how much force is applied to the surface of the planar touch pad member by a user. Processed force sensor signals may indicate the presence of button activity such as press and release events. In response to detected button activity or other activity in the device, actuator drive signals may be generated for controlling the actuator. The user may supply settings to adjust signal processing and tactile feedback parameters.
1. A track pad that receives input from an external object, wherein the track pad does not include a display, the track pad comprising:
a touch pad member having a touch pad sensor array that gathers touch sensor array signals indicative of a given location at which the external object has touched the touch pad member, wherein touch events are registered based on the touch sensor array signals;
a plurality of force sensors each of which is connected to the touch pad member at a different location, wherein the force sensors produce force output signals indicative of how forcefully the external object is pressing on the touch pad member, wherein the force output signals are compared to a threshold to identify press events, and wherein the touch events are registered while the force output signals are below the threshold and while the force output signals are above the threshold; and
an actuator that laterally actuates the touch pad member by imparting global movement to the touch pad member based at least partly on the force output signals.
2. The track pad defined in claim 1 wherein the touch pad sensor array comprises a capacitive touch sensor having an array of capacitive electrodes, wherein each of the plurality of force sensors comprises a piezoelectric force sensor and wherein the touch pad member is mounted at a fixed location within a computer housing by the plurality of force sensors.
3. The track pad defined in claim 1 wherein the actuator comprises at least one coil of wire, wherein the touch pad member is substantially planar and lies in a plane, and wherein the actuator imparts lateral in-plane movement to the touch pad member.
4. The track pad defined in claim 1 wherein the touch pad member is substantially planar and has edges and wherein the actuator comprises a solenoid with a plunger that imparts movement to one of the edges.
5. The track pad defined in claim 1 wherein the touch pad member comprises a rigid substantially planar structure that has an edge and wherein the actuator is coupled to the edge and moves the touch pad member by imparting lateral in-plane force to the edge.
6. The track pad defined in claim 1 , wherein the actuator comprises an electromagnetic actuator that is controlled by a drive signal, wherein the touch pad member comprises a rigid touch pad member that lies in a plane, wherein the touch pad member has left, right, rear, and front edges, wherein the left and right edges are shorter than the rear and front edges, wherein the actuator is coupled to a selected one of the left edge and the right edge, and wherein the actuator moves the touch pad member horizontally within the plane without moving the touch pad member vertically out of the plane.
7. The track pad defined in claim 6 wherein the touch pad member comprises a rigid rectangular member that is globally actuated by the actuator and wherein the plurality of force sensors comprises four force sensors each of which is located at a respective corner of the touch pad member and each of which produces a separate analog force output signal indicative of how forcefully the external object is pressing on the touch pad member, the track pad further comprising:
flexible pads coupled to each of the four force sensors, wherein the flexible pads comprise gel and wherein the force sensors comprise piezoelectric force sensors.
8. The track pad defined in claim 1 wherein the touch pad member comprises a substantially planar rigid rectangular member having edges, wherein the actuator imparts movement to one of the edges, and wherein the plurality of force sensors comprises four force sensors each of which is located at a respective corner of the touch pad member and produces a separate analog force output signal indicative of how forcefully the external object is pressing on the touch pad member.