Power management for interface devices applying forces
A method and apparatus for providing safe and low-cost force feedback peripherals for consumer applications. A device microprocessor local to an interface device is coupled to the host by a first interface bus. The microprocessor receives host commands from the host computer on the first interface bus, such as an RS-232 interface, and commands an actuator to apply a force to a user object, such as a joystick, in response to host commands. A sensor detects positions of the user object and output signals to the host on a second interface bus, such as a PC game port bus, separate from the first bus. In a “recoil” embodiment, a user initiates force feedback by pressing a button on the joystick, which sends an activation signal to the actuator. In other recoil embodiments, the host computer can transmit one or more enable signals and/or activation signals to the actuator to enable or command forces. A safety switch of the present invention disables the actuator when the interface device is not in use and enables the actuator when an amount of weight over a predetermined amount is placed on the joystick created by a user grasping the joystick a circuit of the present invention includes a capacitor for storing power provided by an input signal and supplied to the actuator when forces are to be output.
1. An interface apparatus for interfacing motion of a user manipulable object with a host computer and enabling said host computer to track motion of said user manipulable object and to command feedback forces to said user manipulable object, said interface apparatus comprising:
a user object being physically contacted and manipulable by a user and having at least one degree of freedom of movement with respect to a ground surface;
a device microprocessor provided local to said interface apparatus and separate from said host computer and being controlled by software instructions stored in a memory device separate from said host computer, said microprocessor being coupled to said host computer by a first interface bus and receiving host commands from said host computer on said first interface bus;
an actuator coupled to said user object for applying a force along said degree of freedom to said user object, wherein said actuator applies said force in response to microprocessor force commands produced by said device microprocessor;
a sensor coupled to said user object for detecting a position of said user object along said degree of freedom and for outputting a locative sensor signal which represents said position of said user manipulable object, said locative sensor signal being received by said host computer, wherein said host computer modifies a displayed process in response to said locative sensor signal; and
a thermal sensor for detecting a temperature of said actuator, said thermal sensor providing a temperature signal to said microprocessor such that said microprocessor can deactivate said actuator when said temperature of said actuator rises above a predetermined threshold.
2. An interface apparatus as recited in claim 1 wherein said first interface bus is a serial interface bus for transmitting and receiving data serially.
3. An interface apparatus as recited in claim 2 wherein said first interface bus is an RS-232 interface bus coupled to an RS-232 interface port of said host computer.
4. An interface apparatus as recited in claim 3 wherein said user object includes a joystick.
5. An interface apparatus as recited in claim 3 wherein said sensor is a first sensor and said locative sensor signal is a first locative sensor signal, and further comprising a second sensor coupled to said device microprocessor, wherein said first sensor outputs said first locative sensor signal to said host computer on said first interface bus, and wherein said second sensor detects said position of said joystick along said degree of freedom independently of said first sensor and outputs a second locative sensor signal to said microprocessor.
6. An interface apparatus as recited in claim 5 further comprising a button device coupled to said interface apparatus, said button device providing a button input signal to said microprocessor when said user activates said button, said microprocessor providing said button input signal to said host computer using said game port interface bus.
7. An interface apparatus as recited in claim 6 wherein said microprocessor, said first sensor, said second sensor, and said button are powered by said host computer using a power line of said RS-232 interface bus.
8. A force feedback interface device as recited in claim 2 further comprising a power store circuit coupled to said actuator, said power store circuit storing power from a power source and providing said stored power to said actuator when said actuator applies said force to said user object, said power store circuit including a capacitor that charges to store said power and discharges said stored power for said actuator.
9. An interface apparatus as recited in claim 4 wherein said microprocessor deactivates said actuator when said bus is disconnected from said host computer or disconnected from said interface apparatus.
10. An interface apparatus as recited in claim 4 further comprising a safety switch for said user, wherein said actuator is operative to output said force only when said safety switch is closed.
11. An interface apparatus as recited in claim 10 wherein said safety switch is a hand-weight safety switch coupled to said joystick, said hand weight safety switch being closed by said user when said user applies weight to said joystick by grasping said joystick.
12. An interface apparatus as recited in claim 4 wherein said joystick includes a safety break-away handle that breaks off from said interface apparatus when a force over a predetermined threshold is applied to said joystick.
13. An interface apparatus as recited in claim 12 wherein said safety break-away handle is attached to said interface apparatus by a magnet.
14. An interface apparatus as recited in claim 5 further comprising a local memory device separate from said host computer, said local memory device storing at least one force routine, wherein said microprocessor selects a force routine in accordance with said at least one of said host commands, said force routine determining said microprocessor force commands, at least in part, from said sensor signals of said microprocessor sensors.
15. An interface apparatus as recited in claim 1 wherein said selected force routine retrieves a plurality of digital force values stored in said local memory device and outputs said stored force values to said actuator.
16. An interface apparatus for interfacing motion of a user manipulable object with a host computer and enabling said host computer to track motion of said user manipulable object and to command feedback forces to said user manipulable object, said interface apparatus comprising:
a user object being physically contacted and manipulable by a user and having at least one degree of freedom of movement with respect to a ground surface;
a device microprocessor provided local to said interface apparatus and separate from said host computer and being controlled by software instructions stored in a memory device separate from said host computer, said microprocessor being coupled to said host computer by a first interface bus and receiving host commands from said host computer on said first interface bus, said first interface bus being a serial RS-232 interface bus coupled to an RS-232 interface port of said host computer and configured to transmit and receive data serially;
an actuator coupled to said user object for applying a force along said degree of freedom to said user object, wherein said actuator applies said force in response to microprocessor force commands produced by said device microprocessor; and
a sensor coupled to said user object for detecting a position of said user object along said degree of freedom and for outputting a locative sensor signal which represents said position of said user manipulable object, said locative sensor signal being received by said host computer, wherein said host computer modifies a displayed process in response to said locative sensor signal,
wherein said user object includes a joystick that includes a safety break-away handle attached to said interface apparatus by a magnet, the safety break-away handle being configured to breaks off from said interface apparatus when a force over a predetermined threshold is applied to said joystick.
17. An interface apparatus as recited in claim 16 wherein said sensor is a first sensor and said locative sensor signal is a first locative sensor signal, and further comprising a second sensor coupled to said device microprocessor, wherein said first sensor outputs said first locative sensor signal to said host computer on said first interface bus, and wherein said second sensor detects said position of said joystick along said degree of freedom independently of said first sensor and outputs a second locative sensor signal to said microprocessor.
18. An interface apparatus as recited in claim 17 further comprising a button device coupled to said interface apparatus, said button device providing a button input signal to said microprocessor when said user activates said button, said microprocessor providing said button input signal to said host computer using said game port interface bus.
19. An interface apparatus as recited in claim 18 wherein said microprocessor, said first sensor, said second sensor, and said button are powered by said host computer using a power line of said RS-232 interface bus.
20. A force feedback interface device as recited in claim 16 further comprising a power store circuit coupled to said actuator, said power store circuit storing power from a power source and providing said stored power to said actuator when said actuator applies said force to said user object, said power store circuit including a capacitor that charges to store said power and discharges said stored power for said actuator.
21. An interface apparatus as recited in claim 16 further comprising a thermal sensor for detecting a temperature of said actuator, said thermal sensor providing a temperature signal to said microprocessor such that said microprocessor can deactivate said actuator when said temperature of said actuator rises above a predetermined threshold.
22. An interface apparatus as recited in claim 17 wherein said microprocessor deactivates said actuator when said bus is disconnected from said host computer or disconnected from said interface apparatus.
23. An interface apparatus as recited in claim 1 further comprising a safety switch for said user, wherein said actuator is operative to output said force only when said safety switch is closed.
24. An interface apparatus as recited in claim 23 wherein said safety switch is a hand-weight safety switch coupled to said joystick, said hand weight safety switch being closed by said user when said user applies weight to said joystick by grasping said joystick.
25. An interface apparatus as recited in claim 17 further comprising a local memory device separate from said host computer, said local memory device storing at least one force routine, wherein said microprocessor selects a force routine in accordance with said at least one of said host commands, said force routine determining said microprocessor force commands, at least in part, from said sensor signals of said microprocessor sensors.
26. An interface apparatus as recited in claim 16 wherein said selected force routine retrieves a plurality of digital force values stored in said local memory device and outputs said stored force values to said actuator.