Abstract:
A transmission range selector system having a driver interface module, an electronic control module, and an actuator coupleable to an automotive transmission. The driver interface module may be positioned in a plurality of desired transmission gear positions. The desired gear position set at the driver interface module is redundantly sensed by the combination of a rotational position Hall effect sensor and a plurality of discrete position Hall effect sensors. The rotational position Hall effect sensor has a linearly varying output representative of the desired gear position. The Hall effect sensors provide an output to the electronic control module for energizing the actuator to change the transmission gear position to the desired transmission gear set at the driver interface module. The actuator may include multiple motors to provide redundancy and a sensor gear for providing transmission gear position feedback to the electronic control module.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of co-pending U.S. provisional patent application serial No. 60/147,713 filed Aug. 6, 1999, the teachings of which are incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates in general to electromechanical actuators, and, in particular to transmission range selection system including an actuator for controlling the gear position of an automotive transmission through a driver interface and an electronic control module. 
     BACKGROUND OF THE INVENTION 
     Conventional automobile transmissions are controlled through a gear shift assembly connected to the transmission through a mechanical linkage. The gear shift is normally prominently positioned adjacent the driver&#39;s seat for easy access. In a vehicle having either an automatic or a manual transmission, to change the transmission gear position the operator moves the gear shift to a position corresponding to the intended gear position, e.g., park, neutral, drive, reverse, etc. 
     Unfortunately, known mechanical transmission gear shift assemblies occupy a significant amount of passenger compartment space. Compartment space has always been a valuable commodity in automobile design. With the introduction of new features and technologies to automobiles, compartment space is becoming increasingly valuable. 
     For example, many automobiles today include cellular phones, computerized global positioning systems, increased storage area, etc. Future automobile designs will likely include full computer displays and associated equipment. All of the equipment related to new technologies introduced into automobile designs must be positioned in the already limited space adjacent the driver&#39;s seat. It is recognized, therefore, that reducing the size and space requirements of conventional transmission shift assemblies would be highly beneficial in terms of providing additional space adjacent the driver for the introduction of new equipment. 
     There is, therefore, a need in the art for a compact, cost-effective, and reliable transmission range selector system that may be conveniently operated and efficiently assembled to an automobile. 
     SUMMARY OF THE INVENTION 
     The present invention is organized about the concept providing a compact, cost-effective, and reliable transmission range selector system that may be conveniently operated and efficiently assembled to an automobile. A transmission range selector system consistent with the invention may include a driver interface module, an electronic control module, and an actuator coupleable to an automotive transmission. In one embodiment, the driver interface module may be positioned in a plurality of desired transmission gear positions. The desired gear position set at the driver interface module is redundantly sensed by the combination of a rotational position Hall effect sensor and a plurality of discrete position Hall effect sensors. The rotational position Hall effect sensor may have a linearly varying output representative of the desired gear position. The Hall effect sensors provide an output to the electronic control module for energizing the actuator to change the transmission gear position to the desired transmission gear set at the driver interface module. The actuator may include multiple motors to provide redundancy and a sensor gear for providing transmission gear position feedback to the electronic control module. 
     In particular, a system consistent with the present invention may include: a driver interface module including a portion moveable to a plurality of desired gear positions; at least one sensor for providing an associated output signal in response to movement of the portion to at least one of the desired gear positions; and an actuator for positioning the transmission in at least one of the desired gear positions in response to the output signal. The driver interface module may include an axle that rotates with movement of the movable portion and a magnet disposed on an end of the axle, and the sensor may be a rotational position Hall effect sensor disposed adjacent the magnet. The magnet may be disposed eccentrically on the end of the axle to provide a linearly varying output signal having distinct voltage levels associated with each of the desired gear positions. The actuator may be configured to move the transmission to a respective one of the desired gear positions associated with each of the distinct voltage levels. 
     The system may also include a plurality of discrete position Hall effect sensors, and the movable portion of the interface module may be a shaft having a magnet disposed thereon. The magnet may be disposed adjacent a respective one of the discrete position Hall effect sensors when shaft is in each of the plurality of positions. Each of the discrete position Hall effect sensors may provide a distinct output signal associated with a respective one of the desired gear positions. The actuator may be configured to move the transmission to a respective one of the desired gear positions in response to each of the distinct output signals. 
     The actuator may include at least one electric motor for driving a gear train in response to the output signal. The gear train may include an output gear having output shaft for moving the transmission to the desired gear positions and a sensor gear, the sensor gear having a magnet disposed eccentrically on an end thereof. At least one Hall effect sensor may be disposed adjacent the magnet for providing an actuator output signal representative of the rotational position of the output shaft. The output signal may vary substantially linearly with rotation of the sensor gear. First and second electric motors and first and second Hall effect sensors may be used to provide redundancy. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     For a better understanding of the present invention, together with other objects, features and advantages, reference should be made to the following detailed description which should be read in conjunction with the following figures wherein like numerals represent like parts: 
     FIG.  1 : is a block diagram of an exemplary transmission range selector system consistent with the present invention; 
     FIG.  2 : is front right perspective view of an exemplary driver interface module consistent with the present invention; 
     FIG.  3 : is an exploded view of an exemplary driver interface module consistent with the present invention; 
     FIG.  4 : is a front left perspective view of an exemplary driver interface module consistent with the present invention wherein a housing cover is removed in exploded view; 
     FIG.  5 : is a rear right perspective view of an exemplary driver interface module consistent with the present invention wherein a top cover and a right side cover are removed in exploded view; 
     FIG.  6 : illustrates in diagrammatic the relative positioning of rotational and discrete position Hall effect sensors to associated magnets in an exemplary embodiment consistent with the present invention; 
     FIG.  7 A: illustrates in diagrammatic form the output voltage of a rotational position Hall effect sensors vs. shaft position in an exemplary embodiment consistent with the present invention; 
     FIG.  7 B: illustrates in diagrammatic form the output voltages of discrete position Hall effect sensors vs. shaft position in an exemplary embodiment consistent with the present invention; 
     FIG.  8 : is a perspective view of an exemplary actuator consistent with the present invention; 
     FIG.  9 : is an exploded view of an exemplary actuator consistent with the present invention; 
     FIG.  10 : is a partial exploded view of an exemplary actuator consistent with the present invention; 
     FIG.  11 : is a flow chart illustrating a method of calibrating a system consistent with the present invention; and 
     FIG.  12 : is a block diagram illustrating an exemplary electronic control module for a transmission range selector system consistent with the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to FIG. 1, there is shown a block diagram of an exemplary transmission range selector system  10  consistent with the present invention. As shown, the system includes a driver interface module  12  (hereinafter “DIM”), an electronic control module  14  (hereinafter “ECM”), and an actuator  16  mounted to an automobile transmission  18 . For ease of explanation, the invention will first be described in broad general terms, with a more detailed description of the features and advantages to follow. 
     Generally, the DIM  12  includes a shift accessible to the driver. The shift may be positioned by the driver to designate a desired transmission gear position, e.g. “P” for park, “R” for reverse, “N” for neutral, “D” for drive, etc. The DIM  12  includes position-sensing electronics, e.g., Hall effect sensors, which provide an output signal to the ECM  14  that is representative of the desired transmission gear position selected by the driver at the DIM. The ECM, in turn, provides an output signal to the actuator  16 . 
     The actuator  16  may be mounted directly to the automobile transmission  18 , and, in response to the ECM output, changes the transmission gear position to the position designated by the driver. The actuator  16  also includes position-sensing electronics, e.g., Hall effect sensors, which provide an output to the ECM  14  corresponding to the actual transmission gear position. The ECM output signal may be provided to the actuator  16  on the basis of the desired transmission gear position set at the DIM  12  and the actual transmission gear position from the actuator  16 . 
     Advantageously, the electromechanical system  10  requires significantly less space than the conventional purely mechanical transmission range selector systems. In one embodiment, the DIM and the ECM may be combined to form a single module that may be installed directly to an automobile dashboard. In many automobiles, this can provide significant additional space for other automobile systems. 
     Turning now to FIGS. 2 and 3, there is shown an exemplary embodiment of a DIM  12  according to the invention. With reference particularly to the exploded view of FIG. 3, the DIM  12  generally includes: a housing  20 ; a shaft  22  including a tap up/down spring yoke portion  68 ; an axle  24  having a magnet  25  eccentrically mounted thereon; a magnet  26  mounted to the shaft  22 ; a handle housing  28 ; a button  30  and bell crank  32  assembly on the handle housing  28 ; a handle cover  34 ; a compression spring  60 ; a straw  38  which is depressed by the button  30  and bell crank  32  to release and engage a pawl  40  with pawl gates  41  on the housing  20 ; a detent assembly  42  for resisting motion of the shaft when in a desired position; a solenoid  44  operable through a linkage arm assembly  46  for maintaining the shaft  22  in a “Park” position when the vehicle is turned off; a right side cover  48 ; a shaft guide plate  50 ; a cover  56 ; an opening  74  in the housing  20  to allow the magnet  26  to extend therethrough, an opening  70  in the housing  20  to allow axle  24  and magnet  25  to extend therethrough; a tap up/down yoke  68 ; and a tap up/down spring  62  disposed between knobs  64  and  66 . In addition, in the depicted embodiment, the ECM  14  is secured in the housing  20  in slots  62 A and  62 B. The ECM includes discrete position Hall effect sensors  80   a - 80   d , rotational position Hall effect sensor  82 , and control electronics, as will be described in detail below. 
     With reference also to FIGS. 4 and 5, an operator moves the shaft  22  to a desired gear position (e.g. “P” “R”, “N”, “D”) as indicated on the cover  56  by depressing the button  30 . The button  30  operates through the bell crank  32  to release the pawl  40  from a pawl gate  41  on the housing  20 . With the pawl  40  released from the pawl gate  41 , the shaft  22  may rotate with the axle  24 , which has ends rotatingly disposed in openings  70  and  72  formed in the housing  20  and right side cover  48 , respectively. 
     Rotation of the shaft  22  and axle is detented by the engagement of the detent assembly  42  with detent steps formed in right side cover  48 . When the desired gear position is reached, the button  30  is released and the pawl  40  engages an associated pawl gate  41  to prevent further rotation of the shaft  22 . 
     The shaft  22  is thus positionable at discrete locations between a “Park” position and a “Drive” position. When the shaft  22  is in the “Drive” position, the operator can urge the shaft in a sideward motion, causing the shaft to move from laterally from a discrete gear section  57  of the cover to a tap up/down  59  section of the cover. When the shaft moves into the tap up/down section, the system  10  enters a tap up/down transmission mode, which will be described in greater detail below. In this mode, first  67 and second  69  arms the tap up/down yoke portion  68  are disposed adjacent contact knobs  66 ,  64 , respectively for urging the shaft toward the center of the tap up/down section  59 . Movement of the shaft in a forward or reverse direction thus occurs against the bias of the spring  62  coupled between the knobs  66 , 64 . 
     In operation, when the shaft is positioned in the discrete gear section  57  of the cover, the shaft is positionable in a desired gear position. In illustrated exemplary embodiment, the desired gear position is communicated to the ECM  14  through Hall effect sensing, e.g. through a combination of discrete position Hall effect sensors  80   a - 80   d  and the rotational position Hall effect sensors  82 . The Hall effect sensor  82  produces a linear output as the axle  24  is rotated, and the Hall effect sensors  80   a - 80   d  produce associated digital outputs as the shaft  22  is rotated. As shown, the Hall effect sensors  80   a - 80   d ,  82  may be mounted directly to the ECM. It will be understood by those skilled in the art, however, that other configurations are possible. For example, the ECM could be mounted in a remote position with the hall sensors  80   a - 80   d  and  82  mounted to a printed circuit board in the DIM. 
     Turning now to FIG. 6 the relative positioning of Hall effect sensors  80   a - 80   d  and  82  to magnets  26  and  25 , respectively, is illustrated in diagrammatic form for an exemplary embodiment consistent with the invention. As shown, the magnet  25  is positioned eccentrically relative to the end of the axle  24 . The sensor  82  may be positioned on the ECM to be disposed beneath the magnet  25 . As is known, the output of a conventional Hall effect sensor is dependent on the strength and direction of the magnetic flux adjacent thereto. Those skilled in the art will recognize, therefore, that the magnet  25  need not be positioned precisely beneath the magnet  25 , and that some distance between the magnet  25  and the sensor may be provided depending on the strength of the magnet  25  and the sensitivity of the sensor. 
     Due to the eccentric positioning of the magnet  25  on the axle  24 , the sensor  82  provides a substantially linear output in the range of motion of the shaft  22 . FIG. 7A, for example, illustrates the voltage output of the sensor  82  vs. shaft angle θ for an exemplary embodiment. The sensor output changes in a substantially linear fashion as the shaft is moved through a range of angles θ corresponding to desired gear positions (P, R, N, +, D, −). This linear output allows for highly accurate gear position tracking. In addition, the linear output allows for anticipation of desired gear position by the ECM, thereby allowing the ECM to energize the actuator for achieving the desired position even before the desired position is fully reached at the DIM. 
     For example, if the sensor output is at an intermediate voltage V i  and is changing in a positive direction between a voltage V P  corresponding to a Park position and a voltage V R  corresponding to a Reverse position, then it may be assumed that the operator is moving to a Reverse position from Park. The ECM may thus energize the actuator to begin movement of the transmission to Reverse before the sensor output reaches V R . In a similar manner, active braking of the actuator may also be achieved based on the linear hall output. 
     Redundant position sensing is provided via the magnet  26 , which is positioned in a fixed location relative on the shaft, e.g., as shown in FIG. 3, and the sensors  80   a - 80   d . The sensors  80   a - 80   d  are disposed at discrete positions on the ECM in an arc coinciding with the range of motion of the magnet  26  through an angle θ. Thus, the magnet  26  is positioned successively adjacent the sensors  80   a ,  80   b ,  80   c , and  80   d  when the shaft is in the “Park”, “Reverse”, “Neutral”, and “Drive” positions, respectively. 
     Each sensor may be positioned such that it provides a digital “1” output only when the magnet  26  is positioned immediately adjacent thereto. Curves  81   a ,  81   b ,  81   c , and  81   d  in FIG. 7B, for example, illustrate the sensor output voltage vs. shaft angle θ for the sensors  80   a ,  80   b ,  80   c , and  80   d , respectively. As shown, sensors  80   a ,  80   b ,  80   c , and  80   d  provide a discrete output signal such as a digital “1” to the ECM only when the magnet is positioned a gear position associated with the sensor, thereby indicating that the shaft  22  is positioned at the desired gear position. 
     Thus, when a desired gear position is reached, both the hall sensor  82  and one of the hall sensors  80   a - 80   d  provide an output to the ECM indicating that the shaft  22  is in a specific desired gear position. Based on these output signals, the ECM energizes the actuator  16  to move the transmission from its present gear position to the gear position indicated by the sensors. Advantageously, in the event that either the hall sensor  80  or  82  fails, the remaining sensor will provide the necessary output to the ECM to achieve the desired gear position. 
     In the tap up/down transmission mode, the magnet  25  located on the axle  24  remains in close proximity to the Hall effect sensor  82  on ECM  14 . As discussed above, the sensor  82  provides a linear output depending on the rotational position of the axle. In the tap up/down transmission mode, if the shaft is moved in a forward direction, e.g. toward “+” on the cover  56 , then the output of the sensor  82  will move to a corresponding voltage, e.g. V +  in FIG.  7 A. In response to this output from the sensor, the ECM  14  signals the actuator  16  to shift the transmission  18  up one gear. The shaft  22  is then returned to a central position between “+” and “−” in the portion  59  of the cover under the bias the spring  62  against the yoke  68 . Each forward rotation of the shaft  22  causes the transmission  18  to shift up one gear until it reaches the highest gear. Likewise, rearward rotation, e.g. toward “−” on the cover  56 , causes the sensor output to move to a corresponding voltage, e.g. V −  in FIG.  7 A. In response to this output the ECM  14  signals the actuator  16  to shift the transmission  18  down one gear. Each rearward rotation of the shaft  22  causes the transmission  18  to shift down one gear until it reaches the lowest gear. 
     The highly accurate position sensing provided by sensor  82  and magnet  25  and the redundancy provided by sensors  80   a - 80   d  and  82  thus provide significant advantages. Other sensor configurations are possible. For example, redundant sensing could be achieved through use of other sensor types, e.g. optical or magneto-resistive sensors. Hall effect sensing, however, provides a robust, accurate, and cost-effective system. 
     Turning now to FIGS. 8,  9 , and  10  there is shown an exemplary actuator consistent with the present invention. As shown in exploded view in FIG.  9  and in partially assembled view in FIG. 10, an exemplary actuator  16  generally includes: a housing  90 ; first  92  and second  94  motors with pinion gears  96 ,  98 , respectively; a compound face gear  102  driven by the motor pinion  96  and  98 ; a compound intermediate spur gear  104  for meshingly engaging pinion gear  106  on the compound face gear  102 ; a magnet  116  eccentrically coupled to a shaft  112  having a sector gear  115  thereon, the sector gear  115  driven by a sector gear  110  coupled to an output sector gear  122 , the output sector gear  122  driven by pinion  132  on the spur gear  104 ; and a printed circuit board  118  with first  120 A and second  120 B Hall effect sensors. The output sector gear  122  for drives an actuator output shaft  123  that extends through opening  130  in the housing cover  124 . A gasket  180  is provided between the housing and housing cover to seal the housing against entry of contaminants. 
     In the illustrated exemplary embodiment the actuator output shaft  123  is driven by the two DC motors  92 ,  94 , through a gear train including the face gear  102 , the compound gear  104 , and the sector gear  122 . The motor pinions  96  and  98  meshingly engage upper and lower teeth on the face gear  102  for driving the face gear in response to DC input from the ECM, e.g. through pins  127  on the ECM and associated connections (not shown) the motor windings. The ECM may control both the speed and direction of the motors. 
     The pinion  106  on the face gear  102  meshingly engages the compound spur gear  104 . The pinion  132  on the compound spur gear  104  drives the sector gear  122  to rotate actuator output shaft  123  that is coupleable to the transmission selector shaft for achieving the desired gear position. The illustrated gear train provides a robust and efficient actuator system, which minimizes the possibility for mechanical failure. Those skilled in the art will, however, recognize that other gear train configurations may be provided in a manner consistent with the invention. 
     In an exemplary embodiment, the two motors may provide an output of 69.4 W (7.67 Nm at 92.1 rpm). Advantageously, this output is provided at a lower current draw for each unit of torque compared to a single motor, and the two motors are available at lower cost than a single larger motor. In addition, redundancy is provided in that the system will fully function, in a degraded mode, using only one of the motors, e.g., if one of the motors fails. A lower actuator profile is also possible using two motors as opposed to a single motor, thereby providing orientation flexibility. An output from the motors, e.g. stator current, can be provided to the ECM to detect when a motor fails. If one of the motors  92  or  94  fails, the ECM may generate an error message advising the operator to seek service. 
     Actuator position sensing is achieved via the Hall effect sensors  120 A and  120 B on printed circuit board  118  and the magnet  116 , which is eccentrically positioned on the end of the shaft  112 . The sector gear  110  drives the shaft  112  through meshing engagement of the sector gear  110  with the sector gear  115 . The rotational position of the magnet  116  is, therefore, directly related to the rotational position of the output sector gear  122  and the position of the output shaft  123  coupled to the transmission. 
     To sense the rotational position of the magnet  116 , the printed circuit board  118  is disposed in the housing with the Hall effect sensors  120 A and  120 B positioned adjacent, e.g. beneath, the magnet  116 . As described above, the eccentric positioning of the magnet  116  on the end of the shaft  112  results substantially linear outputs from the Hall sensors  120 A and  120 B. Based on the linear output of Hall effect sensors  120 A and  120 B, the ECM  14  can accurately ascertain the actual transmission gear position. Two Hall effect sensors  120 A and  120 B are used to provide redundancy. 
     In a system consistent with the invention, the output shaft  123  of the actuator is provided for driving a rotatable transmission selector shaft of an automotive transmission  18 . Those skilled in the art will recognize that the rotational position of the transmission selector shaft must be accurately controlled when selecting each gear in order to prevent premature wear of the transmission. The greater the difference between the actual rotational position of the selector shaft and an ideal position, the greater the wear. In the assembly of a system consistent with the invention to an automobile it is therefore necessary to calibrate the system to the transmission  18  to ensure that the desired gear position selected at the DIM corresponds to an actual gear position in the transmission  18 . 
     FIG. 11 illustrates an exemplary method for accurately calibrating a system  10  consistent with the invention with the rotational position of the transmission selector shaft. As shown, the transmission is placed  200  in a specified gear, for example “Park”, with the actuator output shaft  123  coupled to the transmission selector shaft. The shaft  22  of the DIM is then positioned  210  to correspond to the specified gear at which the transmission is set. In the illustrated embodiment, this may be accomplished by actuating the button  30  and rotating the shaft  22  of the DIM to the corresponding rotational position, for example all the way forward to the “Park” position. 
     The ECM is then signaled  220  to establish a relationship between the DIM position and the actuator position. In the illustrated embodiment, the ECM may store into a memory the rotational position of the actuator output shaft  123  based on the output of the Hall sensors  120 A and  120 B and the position of the DIM shaft based on output of the Hall sensors  80   a - 80   d  and  82 . The process may be repeated  230  for all gears. Alternatively, once the ECM has been signaled to establish one relationship between a DIM position and an actuator position, the ECM can establish a relationship for the other DIM positions and actuator positions, e.g. based on ideal parameters. 
     Turning now to FIG. 12, there is illustrated a block diagram of an exemplary ECM consistent with the invention. The ECM  14  may be mounted directly to the DIM  12  or in a remote location. In general, the ECM energizes the actuator  16  to achieve the desired gear position set at the DIM using the Hall effect outputs from the DIM  14  and the actuator  16 . Those skilled in the art will recognize a variety of ECM configurations for achieving control of a transmission gear position consistent with the invention. It is to be understood, therefore, that the illustrated exemplary embodiment is provided by way of illustration, not of limitations. 
     In the illustrated embodiment, the ECM includes a microprocessor  150  for receiving outputs from sensors  80   a - 80   d  and  82  in the DIM  12  on lines  300  and  301 , outputs from sensors  120 A and  120 B in the actuator  16  on lines  302 ,  304 , and control inputs from other devices on lines  306 - 314  for controlling the ECM output to the actuator  16 . In one embodiment, the microprocessor may be a Siemens C505CA controller with 8-bit enhanced 8051 kernal, 32K OTP RAM, 1.25K RAM, and up to 20 MHz operating frequency. The microprocessor may further include an 8 channel 10 bit A/D converter, integrated CAN 2.0B controller with 15 message objects, and a watchdog timer. A 256 byte external I2C EEPROM  152  may also be provided. The ECM further comprises a power supply  152 , a battery backup  154 , an input interface  156 , a BTSI solenoid drive  158 , a wake-up interface  160 , and a CAN interface  162 . 
     The power supply  152  may be a conventional  5 VDC supply for providing a stable reference voltage from the vehicle&#39;s 12VDC battery. The battery backup provides power to the microprocessor  150  if power from the vehicle battery is unavailable. The BTSI (Brake Transmission Shift Interlock) solenoid drive  158  controls the solenoid in the DIM  12 . The solenoid  44  prevents the shaft  22  in the DIM  12  from being rotated out of the “Park” position unless the operator depresses the brake pedal. The Wake-up interface  160  alerts the ECM  14  that the operator has inserted the key in the ignition and the ECM can now respond to received commands. The shaft  22  in the DIM  12  is also prevented from being rotated out of the “Park” position by the solenoid  44  unless the vehicle keys are in the ignition. The CAN (Controller Area Network) interface  162  is the main communications network between the microprocessor  150  and the vehicle main controller (not shown). The CAN is useful for performing remote diagnostics. 
     The input interface  156  receives vehicle speed input on line  306 , service brake input on line  308 , parking brake input on line  310 , shift enable input on line  312 , calibration input on line  314 , and outputs from sensors  120 A and  120 B on lines  302  and  304 , and provides signals representative of these inputs to the microprocessor  150  on line  318 . The microprocessor  150  uses the “vehicle speed” input to prevent the transmission from being shifted into “Park” or “Reverse” when the vehicle is traveling above a predetermined speed. The microprocessor uses the “service brake” input to help slow the vehicle by down shifting when appropriate. The “park brake” input is used to prevent the vehicle from being driven when the parking brake is applied. The “shift enable” input is used to prevent shifting the transmission gear at an inappropriate time. Each of these inputs may be provided by components external to a system  10  consistent with the invention, and provided directly to the input interface. These inputs can alternatively be received over a vehicle&#39;s data bus. The “calibration” input is provided for establishing a relationship between the rotational position of the actuator  16  and the position of the DIM  14  as discussed above. 
     The ECM  14  controls the speed and direction of the motors  92  and  94  in the actuator  16 , which in turn control the rotational position of the actuator output shaft  123 . A desired gear position is set at the DIM and sensors  80   a - 80   d  provide an output representative of the desired position, as described above. Based on the sensor outputs and the signals provided at the input interface, the ECM provides an output to the motors on line  316  to move the transmission to the desired gear. The outputs of Hall sensors  120 A and  120 B are provided to the microprocessor  150  to indicate the actual gear position of the transmission. Once the desired gear position, as determined from sensors  80   a - 80   d  and  82 , and the actual gear position, as determined from sensors  120 A and  120 B, match, the system is deemed to be in the desired gear position. 
     The illustrated ECM provides many advantageous features. It designed with solid-state technology, including no mechanical relays or switches, hall sensors on the board for reading DIM lever position, and an integrated H-bridge may be provided for driving the actuator. The H-bridge may be a Siemens BTS 780GP that is optimized for DC motor applications. The position of the actuator and the DIM lever may be calculated every 5 or 10 ms to ensure highly responsive control. The ECM may be configured to provide automatic re-calibration of the actuator and DIM due to aging. The ECM may also be configured to signal the operator to seek service if the ECM becomes disabled, e.g. if a motor stator current provided to the microprocessor on line  320  moves beyond a predetermined threshold indicating failure of one or more motors  92 , 94 . 
     The embodiments that have been described herein, however, are but some of the several which utilize this invention and are set forth here by way of illustration but not of limitation. It is obvious that many other embodiments, which will be readily apparent to those skilled in the art, may be made without departing materially from the spirit and scope of the invention.