Patent Application
20060145541
The present invention generally relates to multi-state switching logic, and more particularly relates to methods, systems and devices for generating a multi-position control.
Modern vehicles contain numerous electronic and electrical switches. Vehicle features such as climate controls, audio system controls other electrical systems and the like are now activated, deactivated and adjusted in response to electrical signals generated by various switches in response to driver/passenger inputs, sensor readings and the like. These electrical control signals are typically relayed from the switch to the controlled devices via copper wires or other electrical conductors. Presently, many control applications use a single wire to indicate two discrete states (e.g. ON/OFF, TRUE/FALSE, HIGH/LOW, etc.) using a high or low voltage transmitted on the wire.
To implement more than two states, typically additional control signals are used. In a conventional two/four wheel drive transfer control, for example, four active states of the control (e.g. 2WD mode, auto 4WD mode, 4WD LO mode and 4WD HI mode) as well as a default mode are represented using three to five discrete two-state switches coupled to a single or dual-axis control lever. As the lever is actuated, the various switches identify the position of the lever to place the vehicle in the desired mode. Conventional electric mirror controls similarly use three or more discrete switches to represent directions of mirror movement indicated on a stick or similar controller. Power take-off (PTO) controls also typically contain three or more discrete switches to represent the various states of the PTO device, which is commonly used to power upfitter-installed accessories such as bucket lifts, snow plows, lift dump bodies and the like. Numerous other multi-state switches use multiple discrete switches to represent the various positions of a single or dual-axis control mechanism, which in turn represent the various states of a controlled component of the vehicle.
As consumers demand additional electronic features in newer vehicles, the amount of wiring present in the vehicle continues to increase. This additional wiring occupies valuable vehicle space, adds undesirable weight to the vehicle and increases the manufacturing complexity of the vehicle. There is therefore an ongoing need in vehicle applications to reduce the amount of wiring in the vehicle without sacrificing features. Further, there is a need to increase the number of features in the vehicle without adding weight, volume or complexity commonly associated with additional wiring.
In particular, it is desirable to formulate multi-state switching devices such as those used in 2WD/4WD transfer case controls, electric mirror controls, power take off controls and the like that reduce the cost, complexity and weight associated with multiple input switches, wires and other components. Moreover, it is desirable to create a multi-position control with a return-to-default position using low cost and efficient techniques and components. Furthermore, other desirable features and characteristics will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background.
Systems, methods and devices are described for determining and/or indicating the state of a multi-position actuator. According to one embodiment, a circuit for detecting the state of the multi-position actuator suitably includes two or more switches coupled to the actuator and configured to provide input signals as a function of the state of the actuator. One or more of the switches are ternary (three-state) switches to increase the number of states that can be represented. Control logic receives the input signals from the switches and determines the state of the multi-position actuator as a function of the input signals. This circuit is useful in a number of automotive and other applications, including joysticks, transfer case controls, electric mirror controls, power take off controls and other devices.
The present invention will hereinafter be described in conjunction with the following drawing figures, wherein like numerals denote like elements, and:
The following detailed description is merely exemplary in nature and is not intended to limit the invention or the application and uses of the invention. Furthermore, there is no intention to be bound by any expressed or implied theory presented in the preceding technical field, background, brief summary or the following detailed description.
According to various exemplary embodiments, single and/or multi-axis controls for use in vehicles and elsewhere may be formulated with ternary switches to reduce the complexity of the control. Such switches may be used to implement robust and/or non-robust selection schemes for various types of control mechanisms, including those used for power mirrors, 2WD/4WD selectors, power take off controls and the like.
Turning now to the drawing figures and with initial reference to
Switches 102A-B are any devices capable of providing various logic signals 106, 112A-B to components 104, 110 in response to user commands, sensor readings or other input stimuli. In an exemplary embodiment, switches 102A-B respond to displacement or activation of a lever 108A-B or other actuator as appropriate. Various switches 102A-B may be formulated with electrical, electronic and/or mechanical actuators to produce appropriate ternary output signals onto a wire or other electrical conductor joining switches 102 and components 104, 110, as described more fully below. These ternary signals may be processed by components 104, 110 to place the components into desired states as appropriate. In various embodiments, a single ternary signal 106 may be provided (e.g. between switch 102A and component 104 in
Many types of actuator or stick-based control devices provide several output signals 112A-B that can be processed to determine the state of a single actuator 108B. Lever 108B may correspond to the actuator in a 2WD/4WD selector, electronic mirror control, power take off selector or other device operating within one or more degrees of freedom. Various degrees of movement may be provided with one or more guides that allow a hinged lever to move along an axis, for example, with multiple degrees of movement being provided with two or more guide axes. In alternate embodiments, lever 108A-B moves in a ball-and-socket or other arrangement that allows multiple directions of movement. The concepts described herein may be readily adapted to operate with any type of mechanical selector, including any type of lever, stick, or other actuator that moves with respect to the vehicle via any slidable, rotatable or other coupling (e.g. hinge, slider, ball-and-socket, universal joint, etc.).
Referring now to
Switch 212 is any device, circuit or component capable of producing a binary, ternary or other appropriate output on conductor 106. In various embodiments, switch 212 is a conventional double-throw switch as may be commonly found in many vehicles. Alternatively, switch 212 is implemented with a multi-position operator or other voltage selector as appropriate. Switch 212 may be implemented with a conventional three-position low-current switch, for example, as are commonly found on many vehicles. Various of these switches optionally include a spring member (not shown) or other mechanism to bias an actuator 106 (
Switch 212 is typically configured to select an output from two reference voltages (such as a high reference voltage (e.g. Vref) and a low reference voltage (e.g. ground)), as well as an intermediate value. In an exemplary embodiment, Vref is the same reference voltage provided to digital circuitry in vehicle 100 (
Contacts 212 are therefore operable to provide a ternary signal 106 selected from the two reference signals (e.g. Vref and ground in the example of
The signals 106 produced by contacts 212 are received at a voltage divider circuit 216 or the like at component 104, 110 (
The ternary voltages present at common node 208 are then provided to an analog-to-digital converter 202 to decode and process the signals 204 as appropriate. In various embodiments, A/D converter 202 is associated with a processor, controller, decoder, remote input/output box or the like. Alternatively, A/D converter 202 may be a comparator circuit, pipelined A/D circuit or other conversion circuit capable of providing digital representations 214 of the analog signals 204 received. In an exemplary embodiment, A/D converter 202 recognizes the high and low reference voltages, and assumes intermediate values relate to the intermediate state. In embodiments wherein Vref is equal to about five volts, for example, A/D converter may recognize voltages below about one volt as a “low” voltage, voltages above about four volts as a “high” voltage, and voltages between one and four volts as intermediate voltages. The particular tolerances and values processed by A/D converter 202 may vary in other embodiments.
As described above, then, ternary signals 106 may be produced by contacts 212, transmitted across a single carrier, and decoded by A/D converter 202 in conjunction with voltage divider circuit 216. Intermediate signals that do not correspond to the traditional “high” or “low” outputs of contact 212 are scaled by voltage divider circuit 216 to produce a known intermediate voltage that can be sensed and processed by A/D converter 202 as appropriate. In this manner, conventional switch contacts 212 and electrical conduits may be used to transmit ternary signals in place of (or in addition to) binary signals, thereby increasing the amount of information that can be transported over a single conductor. This concept may be exploited across a wide range of automotive and other applications, as described more fully below in conjunction with
Referring now to
In an exemplary embodiment, voltage divider 308 includes two or more resistors 302 and 304 electrically arranged between common node 208 and the input 306 to A/D converter 202. In
Using the concepts set forth above, a wide range of control circuits and control applications may be formulated, particularly within automotive and other vehicular settings. As mentioned above, the binary and/or ternary signals 106 produced by contacts 212 may be used to provide control data to any number of vehicle components 104, 110 (
As used herein, state 404 is referred to as ‘1’ or ‘high’ and corresponds to a short circuit to Vref, B+ or another high reference voltage. Similarly, state 408 is referred to as ‘0’ or ‘low’, and corresponds to a short circuit to ground or another appropriate low reference voltage. Intermediate state 406 is described as ‘value’ or ‘v’, and may correspond to an open circuit or other intermediate condition of switch 212. In many embodiments, intermediate state 406 is most desirable as a “power off” state, since the open circuit causes little or no current to flow from contacts 212, thereby conserving electrical power. Moreover, an ‘open circuit’ fault is typically more likely to occur than a faulty short to either reference voltage; the most likely faults (open circuits) may therefore result in a less disruptive result, such as turning a feature off rather than leaving the feature ‘stuck’ in an on position should a fault occur. On the other hand, some safety-related features (e.g. headlights) may be configured to remain active in the event of a fault, if appropriate. Accordingly, the various states of contacts 212 described herein may be re-assigned in any manner to represent the various inputs and/or operating states of component 104 as appropriate. The naming and signal conventions used herein are simply for consistency and ease of understanding and may be modified in any manner across a wide array of equivalent embodiments.
Using the concepts of ternary switching, various exemplary mappings of contacts 212 for certain automotive and other applications may be defined as set forth below. Other embodiments may differ from those set forth below, and many additional implementations could be formulated beyond those set forth herein.
Further, the broad concepts of ternary switching can be modified and/or enhanced in any manner. Components that utilize only binary input, for example, could use the third command state provided by circuits 200, 300 above as a diagnostic state. With momentary reference again to
The concepts described above may be readily implemented to create a multi-state actuator driven control. In such embodiments, two or more switches 102/202 are generally arranged proximate to an actuator 108, with the outputs of the switches corresponding to the various states/positions of the actuator. In various embodiments, the outputs of the switches may be processed using conventional logic gates (e.g. AND/NAND, OR/NOR or the like) or processing circuitry to determine the state of the actuator. Actuator 108 may be guided through the various positions by any mechanical structure.
With reference now to
Diagram 500 shows the respective positions of the various states of actuator 108, with diagram 550 showing corresponding contact settings for indicating when the actuator is in each state. Each of the two contacts 212 in this exemplary embodiment are ternary switches capable of producing three discrete outputs corresponding to “low”, “high” and “value” as described above. Using the assumption that open circuits are more likely to be encountered than shorts to ground, which in turn are more likely than shorts to the battery voltage (B+), the exemplary embodiment shown in
As shown in TABLE 1 and
As the operator moves the actuator to indicate desired transitions to other states, the two ternary contacts 212 are actuated and the resulting ternary signals 112 are provided to indicate the current state of the actuator. The state may be determined using conventional logical “AND” constructs, which in turn may be implemented with discrete components, integrated circuitry, software or firmware instructions, and/or in any other manner. As shown in diagram 500, states 1, 3, 5, 7 and 9 of TABLE 1 correspond to the 4H, 2W, default, Auto 4W and 4L positions of the transfer control, respectively. Although other switching schemes could be used in alternate embodiments, by selecting the switching states to correspond to TABLE 1, failures can be minimized since at least two separate failures would be required to improperly transition between states 504 and 510, and/or between states 506 and 508. These state pairs may be appropriately interlocked from each other to further prevent inadvertent transfers from one state to another and to prevent electrical shorts and other performance issues that may arise. Moreover, the control may be made more robust by verifying that actuator 108 moves through default state 502 between any other transitions. Shifting from 4H to 4L, for example, actually involves four switching state transitions (i.e. state 1 (“0-0”) to state 5 (“v-v”), and then state 5 (“v-v”) to state 9 (“1-1”).
TABLE 1 also shows states 2, 4, 6 and 8, which correspond to optional failure states for the transfer control. Although not required in all embodiments, these states can be identified to diagnose shorts or other problems within the switching system. Note that each of the four failure states includes a single “open circuit” reading, meaning if a single “open circuit” is observed, the system may conclude that at least one fault has occurred.
Alternatively, a switching scheme 600 (
By comparing diagram 650 to diagram 600 in view of TABLE 2, it can be seen that “state 2” corresponds to default state 602, with states 1, 3, 4 and 6 corresponding to 4HI state 608, 2WD state 610, Auto4W state 604 and 4LO state 606, respectively. State 5 may be used as a diagnostic state, with a “state 5” reading indicating a fault. Alternatively, state 5 could be used as the default setting, and state 2 could be used as a fault state in an alternate embodiment, although the prior embodiment may be more preferable in many applications due the greater likelihood of a faulty short to ground occurring than a faulty short to the higher reference voltage. Like the scheme shown in TABLE 1, this scheme provides dual transitions for states on opposing sides of the default state to minimize unwanted state transitions resulting from faults or the like. This scheme also places at least one open circuit condition at default state 602 to reduce the amount of parasitic current consumed by the switching circuitry. By verifying that actuator 108 transitions through default state 602, additional robustness is added to the system because additional switching state transitions are required to inadvertently register an incorrect position of actuator 108.
An additional advantage found in various further embodiments using one or more discrete binary switches 102 is that the binary switch need not be physically connected to each state, but may be placed in a “default” high or low state using a pull-up or pull-down resistor to the upper or lower bias voltages, respectively. In the embodiment described in TABLE 2 above, for example, Input1 may be tied to the lower reference voltage (e.g. ground) via a pull-down resistor, thereby eliminating the need to physically couple switch Input1 to states 1, 2 or 3. When the actuator 108 is in default state 602 (“state 2” in Table 2), for example, no electrical contact exists between actuator 108 and Input1 for the proper switching state to register. Conversely, Input1 could be tied to the upper bias voltage with a pull-up resistor to bias the input toward a “high” value and negate the need to couple the switch to states 4, 5 or 6, although this embodiment would not provide the benefit of reducing contacts for the default state. Similar concepts may be applied to other embodiments using binary switches, including the embodiments shown in
Additional robustness may be designed into the switching system through any technique. In various embodiments, an additional (e.g. third) contact is provided to further improve the reliability and robustness of the switching scheme. With reference now to
As shown in TABLE 3, when actuator 108 is in default state 902, all three input switches produce an open circuit to reduce parasitic current flow. Also, TABLE 3 shows that any desired or undesired transition from one state to another would require at least two state changes (in addition to the changes involved in transitioning through the default state), thereby reducing the likelihood of a device failure and improving the safety of the control. Still further, the configuration shown in TABLE 3 has been structured such that the most safety-sensitive transition (e.g. from “off” to “on” and vice versa) is defined with three separate state transactions (e.g. 0-v-0to v-1-1) such that all three switches must change state for the transition to register, thereby inadvertent turn-ons or shut-offs are even less likely.
An alternate embodiment of a three-switch, five-state control is shown in
Like the embodiment shown in TABLE 3, each state transition in TABLE 4 requires two relatively simultaneous transitions, thereby reducing the likelihood of a false transition. Moreover, even more robustness is provided by this embodiment, since any accidental transition from the default to another position would require a transition to either a “0” or “1” state, which is much less likely to occur in practice than a transition to an open circuit (“v”). Accordingly, the scheme shown in TABLE 4 is highly robust. This robustness can be further enhanced by verifying that actuator 108 passes through default state 1002 between each other state transition, thereby requiring even more switch transitions.
With reference now to
To maintain the robustness of the control mechanism, the various actuator states may be assigned as shown in TABLE 5:
Alternatively, the various actuator states may be configured as in TABLE 6 without sacrificing robustness. This embodiment is shown in
Each of the embodiments described herein may be modified in a variety of ways. Different actuator positions could be logically associated with similar signal combinations, for example, or the various signal combinations could be modified in any manner. The various positions of actuator 108 may be extracted and decoded through any type of processing logic, including any combination of discrete components, integrated circuitry and/or software. Moreover, the various positional and switching structures shown in the figures and tables contained herein may be modified and/or supplemented in any manner.
Although the various embodiments are most frequently described with respect to automotive applications, the invention is not so limited. Indeed, the concepts, circuits and structures described herein could be readily applied in any commercial, home, industrial, consumer electronics or other setting. Ternary switches and concepts could be used to implement a conventional joystick, for example, or any other pointing/directing device based upon four or more directions. The concepts described herein could therefore be readily applied in aeronautical, aerospace, marine or other vehicular settings as well as in the automotive context.
While at least one exemplary embodiment has been presented in the foregoing detailed description, a vast number of variations exist. The various circuits described herein may be modified through conventional electrical and electronic principles, for example, or may be logically altered in any number of equivalent embodiments without departing from the concepts described herein. The exemplary embodiments described herein are intended only as examples, and are not intended to limit the scope, applicability, or configuration of the invention in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing one or more exemplary embodiments. Various changes can therefore be made in the functions and arrangements of elements set forth herein without departing from the scope of the invention as set forth in the appended claims and the legal equivalents thereof.
