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. An electronic device comprising:
storage and processing circuitry; and
a track pad coupled to the storage and processing circuitry, wherein the track pad has an active surface and a touch pad member that extends across substantially all of the active surface, a touch sensor array coupled to the touch pad member, force sensors coupled to the touch pad member that produce force sensor signals indicative of how forcefully an external object is pressing on the touch pad member, and an actuator coupled to the touch pad member that produces tactile feedback by moving the touch pad member in response to the force sensor signals, wherein the storage and processing circuitry is configured to use the touch sensor array to detect gesturing activity on the track pad by identifying gesturing movement across the active surface of the track pad and is configured to momentarily inhibit movement of the touch pad member by the actuator in response to detecting the gesturing activity, wherein the gesturing movement across the active surface of the track pad is associated with multiple locations on the active surface of the track pad.
2. The electronic device defined in claim 1 wherein the touch pad member has four edges and lies substantially in a plane and wherein the actuator is coupled to one of the edges and moves the touch pad member substantially within the plane.
3. The electronic device defined in claim 2 wherein the storage and processing circuitry comprises force signal processing circuitry that process the force sensor signals to produce press and release data indicative of when a user has pressed and released a finger contacting the touch pad member.
4. The electronic device defined in claim 3 wherein the force sensors comprise piezoelectric sensors.
5. The electronic device defined in claim 3 further comprising:
a plurality of flexible pads, each of the flexible pads being coupled to a respective one of the force sensors.
6. The electronic device defined in claim 5 further comprising:
housing structures, wherein the plurality of flexible pads are mounted to the housing structures.
7. The electronic device defined in claim 6 wherein the housing structures include a computer housing wall to which the flexible pads are attached.
8. The electronic device defined in claim 6 further comprising coupling structures coupled between the actuator and the touch pad member.
9. The electronic device defined in claim 8 wherein the coupling structures comprise an elongated metal member.
10. The electronic device defined in claim 9 wherein the elongated metal member has portions comprising a bend.
11. The electronic device defined in claim 8 wherein the coupling structures comprise a mechanical linkage.
12. The electronic device defined in claim 11 wherein the mechanical linkage comprises at least one member and at least one pivot about which the member rotates.
13. The electronic device defined in claim 1 wherein the storage and processing circuitry is configured to receive user-defined force signal processing settings.
14. The electronic device defined in claim 1 wherein the touch sensor array produces touch data and wherein the storage and processing circuitry is configured to receive first user-defined settings that control how the storage and processing circuitry processes the force sensor signals and is configured to receive second user-defined settings that control how the storage and processing circuitry processes the force sensor signals.
15. A method of operating a computer track pad that has a touch pad member with a touch sensor array, force sensors connected to the touch pad member, and an actuator, comprising:
with the touch sensor array, determining a location of an external object in contact with the touch pad member of the track pad;
with each of the force sensors, measuring how much force is applied to the touch pad member of the track pad with the external object to produce data relative to how much force is applied to the touch pad member;
with the actuator, imparting global movement to the touch pad member of the track pad based at least partly on the data gathered with the force sensors, wherein the actuator is driven by actuator drive signals to impart the movement to the touch pad member of the track pad; and
adjusting the actuator drive signals based at least partly on user-defined driver settings.
16. The method defined in claim 15 further comprising:
gathering the user-defined driver settings; and
when imparting movement to the touch pad member of the track pad, generating the actuator drive signals based at least partly on the user-defined driver settings.
17. The method defined in claim 16 wherein the user-defined driver settings include settings specifying use of asymmetric actuator drive signals having faster rise times than fall times.
18. The method defined in claim 16 wherein the user-defined driver settings include settings specifying use of asymmetric actuator drive signals having faster fall times than rise times.
19. The method defined in claim 18 wherein the user-defined driver settings further include settings specifying use of symmetric actuator drive signals having substantially equal rise and fall times.
20. The method defined in claim 18 wherein there are four of the force sensors each of which is located under a respective corner of the touch pad member of the track pad, wherein the force sensor signals comprise analog force sensor signals, and wherein measuring how much force is applied to the touch pad member of the track pad comprises:
gathering separate analog force sensor signals from each of the four force sensors; and
combining the analog force sensor signals that have been gathered.
21. The method defined in claim 20 wherein combining the analog force sensor signals comprises digitally averaging the analog force sensor signals.
22. A computer track pad system, comprising:
a rigid rectangular touch pad member that includes a capacitive touch sensor array and that has four corners;
four force sensors, each force sensor being coupled to a respective one of the four corners;
at least one actuator that is connected to an edge of the rigid rectangular touch pad member by a coupling member and that imparts movement to all of the rigid rectangular touch pad member in response to actuator drive signals; and
circuitry that processes touch sensor data from the capacitive touch sensor array and analog force data from the force sensors and that produces the actuator drive signals for the actuator based on the touch sensor data from the capacitive touch sensor array and based on the analog force data from the force sensors, wherein each of the four force sensors produces a corresponding analog force signal and wherein the circuitry is configured to process the analog force signals from the four force sensors to produce an average force signal, wherein the circuitry is configured to identify button press and button release activity by processing the average force signal and wherein the button press and button release activity is indicative of forces applied to the rigid rectangular touch member by a user.
23. The computer track pad system defined in claim 22 wherein the circuitry is configured to produce the corresponding actuator drive signals in response to identifying the button press and button release activity.
24. The computer track pad system defined in claim 23 wherein the circuitry is configured to inhibit production of the corresponding actuator drive signals in response to identifying the button press and button release activity when the circuitry detects simultaneous gesture activity with the capacitive touch sensor array.
25. The computer track pad system defined in claim 22 wherein the force sensors include polymer-metal composite force sensors.
26. The computer track pad system defined in claim 22 wherein the force sensors include material that exhibits a change in resistance when force is applied to the force sensors.
27. The computer track pad system defined in claim 22 wherein the force sensors include electrodes that exhibit capacitance changes when force is applied to the force sensors.
28. The computer track pad system defined in claim 22 wherein the force sensors include strain gauges.
29. The computer track pad system defined in claim 22 wherein the rigid rectangular touch pad member comprises:
a rectangular planar layer of glass; and
a layer of opaque ink covering at least one surface of the layer of glass that prevents light from passing through the layer of glass.