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ACTUATOR HAVING ELECTRONICALLY CONTROLLABLE TACTILE RESPONSIVENESS
This application is a continuation application of Ser. No. 08/076,344, filed Jun. 11, 1993, now U.S. Pat. No. 5,414, 337, entitled: ACTUATOR HAVING ELECTRONICALLY CONTROLLABLE TACTILE RESPONSIVENESS, which is a continuation-in-part of application Ser. No. 783,635, filed Oct. 24,1991, now U.S. Pat. No. 5,220,260, issued Jun. 15, 1993.
FIELD OF THE INVENTION
The present invention relates to actuators and in particular to actuators providing tactile feedback and having programmable torque-position profiles.
BACKGROUND OF THE INVENTION
In numerous contexts humans perform tasks by interacting with machines via actuators having knobs, dials or linear actuators. Such human interaction in many instances becomes conditioned upon the responsiveness of the actuator. The human operator interacts in accordance with tactile feedback perceived through contact with the actuator knobs, dials or handles.
For example, in video or film editing using systems as described in U.S. Pat. Nos. 4,937,685 and 4,964,004 which are incorporated herein by reference, an editor edits video image information at a console having a plurality of "control wheels" (i.e. large dials or knobs). The film or video editor controls operation of a composition system from an operator's console, as illustrated in FIG. 1, using two sets of controls, one for each hand, to control the editing process. Each control set includes a plurality of finger switches or pushbuttons 110 clustered proximate to a large rotatable control wheel 112, facilitating tactile operation with minimal hand movement. As the editor is focussing on at least one video monitor, viewing frames of visual source material during the editing function, it is generally the case that the operator will acquire a feel for the various controls and become acclimated to their functionality through tactile feedback therefrom, rather than having to look at the control wheel(s) for visual feedback. Accordingly, more efficient human interaction with, and sensitivity to the composition system is achieved.
The control wheels 112 exhibit tactile responsiveness, such as detents or clicks, as they are rotated. Typically, a full rotation of the wheel 112 is correlated to a unit of time, such as one second, of viewing the visual source material being edited. A corresponding number of "frames" of visual source material will be viewed during such a time period, depending on the medium or type of source material being edited. It is most desirable that the number of frames of source material be correlated to the tactile responsiveness, i.e. number of clicks, of the wheel 12 during rotation. For instance, film editing involves standardized source material of which twenty-four (24) frames are provided per second. Thus, it is most desirable that in a full rotation of the wheel 112 (presenting one second of source material), the wheel respond with twenty-four (24) clicks, each click corresponding to one frame of the visual source material.
While film editing involves source material having twenty-four (24) frames per second, other video medium standards require different frame rates. The frame rate, or number of frames per second according to the National 5 Television System Committee (NTSC) is thirty (30) frames per second, a standard promulgated for television video in the United States. Standards such as PAL and SEC AM provide for a standard frame rate of twenty-five (25) frames per second in England and France respectively. New standards for high definition television specify a frame rate of thirty (30) or sixty (60) frames per second.
Differing frame rate standards relating to visual source material and the nature of mechanical detents in actuators, presents the problem that multiple actuators are required to facilitate correlation between actuator tactile responsiveness and the various visual source material standards. As illustrated in FIG. la, actuators known in the art for providing tactile responsiveness typically incorporate a mechanical detent mechanism. A fixed number of clicks is provided by a spring loaded friction mechanism 111 coacting with a sprocket 113 having a fixed number of cogs or detents corresponding to the desired number of clicks per revolution. Therefore, an actuator having twenty-four fixed detents is required and dedicated for a film editing context, a thirty detent actuator is required for a NTSC video editing system, a twenty five detent actuator is required in the PAL or CCAM video editing context, etc. The plurality of actuators required limits the flexibility of visual source material composition systems and significantly increases the complexity, cost and hardware requirements of a flexible system.
In addition to the lack of flexibility of use of fixed mechanical detent actuators, such actuators disadvantageously become worn and suffer tactile responsiveness degradation over time. Other mechanically/spring loaded linear or rotary actuators suffer similar deficiencies.
SUMMARY OF THE INVENTION
The present invention provides an actuator having electronically controllable tactile responsiveness which is flexibly programmable to facilitate provision in a single actuator of torque-position characteristics, such as a selectable number of detents per actuation through its full operative path. In an illustrative case of a rotary actuator the present invention facilitates provision in a single actuator, of torque versus angular position characteristics, such as a selectable number of detents per revolution.
According to the invention, an actuator is in communication with a servo motor having a position encoder which outputs position information to a controller that has access to torque-position relation information. The output of the controller is a digital torque signal, in accordance with the torque-position relation information, which is converted to an analog current signal applied to the servo motor to generate torque in the servo motor. The torque, presenting a tactile response to a human interacting with the actuator, is sensed as a detent or a plurality of detents.
In further accord with the invention, the controller is a microprocessor which receives position information, from the encoder, through a counter as a position count. Torqueposition relation information is stored in microprocessor accessible firmware as a table containing a series of particular torque values corresponding to a series of particular position values. The torque values, output as digital signals and converted by a digital to analog converter, can be modified in accordance with a plurality of stored torque
versus position tables to facilitate flexible programming of various torque profiles.
Features of the invention include the capacity to store and modify torque profiles and to select one of a predetermined set of torque profiles to provide an actuator with a desired tactile responsiveness. The torque profiles, stored for example, in electrically erasable programmable read only memory can be changed via a computer in communication with the microprocessor. Upon system power down and subsequent power up, a previously entered torque profile can be present as a default profile.
DESCRIPTION OF THE DRAWING
These and other features and advantages of the present invention will become more apparent in view of the following detailed description in conjunction with the accompanying drawing, of which:
FIG. 1 is an illustration of an operator's console for editing visual source material in a composition system;
FIG. la is a partially broken-away view of an actuator according to the prior art having mechanical detents;
FIG. 2 is a block diagram of a system for providing programmable tactile feedback in an actuator;
FIG. 3 is a block diagram of a system for providing programmable tactile feedback in an actuator, wherein the controller comprises a counter, microprocessor and accessible firmware;
FIG. 3a is an illustrative diagram of an actuator and associated function keys for controlling multiple functions and providing multiple tactile responses in accordance with the selected function;
FIG. 4 is a block diagram of a system for providing programmable tactile feedback in an actuator, wherein the system further includes a tachometer sensing motor actuation to generate a corresponding actuation in an associated actuator;
FIG. 5A is a view of a prior art mechanical means for introducing resistance in an exercise machine;
FIG. 5B is a block diagram illustrating implementation of a torque controller according to the invention implemented in an exercise machine; and
FIG. 6 is a block diagram of a joystick implementation of an actuator with electronically controllable tactile responsiveness.
DETAILED DESCRIPTION OF AN
Referring now to FIG. 2, an actuator, such as a rotary actuator having a control knob 114 is attached via a shaft to a servo motor 116. In this illustrative embodiment wherein the actuator is for use in a film/video editing context, the servo motor is a PMI12FVS motor. In the present application, as discussed in greater detail hereinafter, the servo motor is not used as a motor per se, but rather as a torque controller. The motor never runs at a significant amount of its rated revolutions per minute, but operates normally in this application in a stalled or semi-stalled state. The preferred motor 116 has an installed encoder 118. The encoder 118 is a PMI M23, 300 segment modular encoder having an index and providing 300 cycles per revolution, which results in 1200 waveform edges from index to index. Note that in this illustrative embodiment it is important that the encoder be selected to provide a number of edges which is divisible by factors of two, three, five and eight. Thus, position infor
mation can be electronically divided to provide an integer number of clicks in selectable modes of 24, 25 and 30 positions per revolution (corresponding to the film/video editing standards of 24, 25 and 30 frames per second or revolution, as discussed hereinbefore).
The position information received from the encoder 118 is processed by a controller 120 so that it represents a positional count. The controller 120 accesses stored input data 122 in the form of torque-position relation information which correlates a received position count with a related torque value. As noted hereinbefore, the position count, which is a function of encoder output information, can be derived by electronically dividing position information provided by the encoder waveform, as desired into a selected number of positions or position values. The input data 122 accessed by the controller 120 will have stored torque values associated with the selected position values as provided in accordance with the desired torque profile. The controller 120 outputs the torque value as a digital signal which is converted by a latchable digital to analog converter 124 to an analog voltage. As a voltage applied to the motor would result in a proportional motor-speed, the analog voltage is related to motor torque by generating a proportional motor current using a power amplifier 126 in conjunction with a motor power supply 128. The torque related current is applied to the motor 116 to present the desired torque which imparts the desired tactile responsiveness to the control knob 114.
In an embodiment illustrated in FIG. 3, the controller 120 comprises a counter 130 which receives the servo motor position information from the encoder 118. A microprocessor 132, such as a Motorola 6809, receives a position count from the counter 130 providing an indication of servo motor position relative to the index. The count provided by the counter will increment or decrement depending on the direction of the change of position of the servo motor. The microprocessor accesses electrically erasable programmable read only memory 134 (EEPROM) which is programmed with one or more tables of torque-position relation information. Each table defines a particular torque profile specifying a torque value corresponding to a particular position count (i.e. knob/servo motor position).
A main application CPU 136 runs an application which requires and defines particular torque profiles for the actuator 114. The main application CPU may run an application which defines the functionality of a control wheel and related function buttons as illustrated in FIG. 3a. In this illustrative embodiment the control wheel has an outer dial 140 which according to the application performs a first function having a fixed number of positions, such as selecting one of a plurality of switch settings. The application can assign a second function to the same outer dial 140 and provide a profile assigning an alternative responsiveness to the outer dial actuator, such as assigning a lever control function having electronically defined stop positions, when a shift key 142 is depressed. An inner control knob 144 similarly can be assigned a first function and corresponding torque profile (such as a free running non-detent scan function), by the application running on the main application CPU, and a second (or other) function and corresponding torque profile (such as a 30 detent per rotation edit mode, as discussed hereinbefore), which is invoked such as by depressing an alt key 146.
The main application CPU 136, upon application initialization, down loads the desired torque profiles to the microprocessor accessible EEPROM, via an RS-232 serial, or other communication port. The desired torque profiles reside