Patent Publication Number: US-9425729-B2

Title: Motor control devices and methods

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is a non-provisional and claims the benefit of U.S. Pat. Ser. No. 61/788,910, filed Mar. 15, 2013, and incorporated herein by reference. 
    
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH 
     Not applicable. 
     BACKGROUND OF THE INVENTION 
     The present invention generally relates to motor control devices and methods, and more particularly to motor control devices and methods that are applicable with electric motors used in automotive powered device applications. 
     Electrically energized motors are used in a wide variety of applications. For instance, various automotive applications incorporate a motor for actuation of an attached device, such as powered doors, hatches, and liftgates. The operation and control of these powered devices has become increasingly sophisticated, while at the same time economic and packaging constraints continue to present additional challenges. In particular, it would be advantageous to replace structural control mechanisms, such as clutches and positive temperature coefficient (PTC) thermal breakers, with electronic control mechanisms that can be applied without consuming valuable space within or near the motor housing. 
     In light of at least the above design considerations and the challenges presented by them, a need exists for improved motor control devices and methods capable of use in automotive applications. 
     SUMMARY OF THE INVENTION 
     In one aspect, methods and devices manage power generated by mechanical rotation of an electric motor in an automotive application. 
     In another aspect, methods and devices determine and regulate the heat generated by an electric motor. 
     In a further aspect, methods and devices determine and verify the thermal characteristics of an electric motor during electric and manual operation. 
     In yet another aspect, methods and devices operate and control an electric motor after a temperature threshold has been exceeded. 
     In another aspect, methods and devices monitor manual operation of an electric motor in connection with thermal protection of the motor. 
     In a further aspect, methods and devices address thermal protection of an electric motor when available data is insufficient. 
     In yet a further aspect, a hinge arm device and method of manufacture incorporate overlapping flanges that are bonded. 
     In one aspect, the present disclosure provides a method of managing power generation of an electric motor that is in electrical communication with a controller. The method includes monitoring a rotational speed of a drive shaft of the electric motor, comparing the rotational speed to an upper rotational speed threshold, and limiting a voltage on a circuit path between the electric motor and the controller when the rotational speed is greater than the upper rotational speed threshold. The voltage being generated by the electric motor. Limiting the voltage on the circuit path may include electrically connecting a battery to the circuit path such that the voltage on the circuit path is limited to a battery voltage of the battery. Electrically connecting the battery to the circuit path may include clamping the circuit path to the battery such that an excess voltage above the battery voltage is transferred from the electric motor to the battery. 
     The method may further include monitoring the voltage on the circuit path, comparing the voltage to an upper voltage threshold, and limiting the voltage when the voltage is greater than the upper voltage threshold. Monitoring the rotational speed may include receiving the rotational speed from a hall sensor configured to detect the rotational speed of the drive shaft. Monitoring the voltage on the circuit path may include detecting the voltage across a plurality of power lines electrically connecting the controller to the electric motor. Electrically connecting the battery to the circuit path may include closing a relay between the circuit path and the battery. 
     The method may further include detecting that the electric motor has stopped generating an excess voltage and, if the battery is electrically connected to the circuit path, disconnecting the battery from the circuit path when the electric motor has stopped generating the excess voltage. The method may further include detecting that the rotational speed is below a lower rotational speed threshold and, if the battery is electrically connected to the circuit path, disconnecting the battery from the circuit path when the electric motor has stopped generating the excess voltage and/or the rotational speed is below the lower rotational speed threshold. The method may further include determining whether the controller is in electrical communication with the battery and, if the controller is not in electrical communication with the battery, interrupting the electrical communication between the controller and the electric motor. 
     In another aspect, the present disclosure provides a method for preventing damage to a controller of an electric motor in a vehicle having a battery from back electromotive force. The method may include monitoring, in a circuit path, a voltage and a rotational speed generated by back-driving the motor and detecting whether power is supplied to the controller by the battery. If the controller is not powered by the battery, the method includes breaking the circuit path between the controller and the motor. Breaking the circuit path between the controller and the motor may include maintaining a harness relay of the vehicle in an open position, the harness relay controlling a power line between the controller and the motor. If the controller is powered by the battery, the method may include comparing the voltage to an upper voltage threshold, comparing the rotational speed to an upper rotational speed threshold, and, if the voltage exceeds the upper voltage threshold or the rotational speed exceeds the upper rotational speed threshold, clamping the circuit path to the battery to charge the battery with the voltage. The upper voltage threshold may be 18 volts. 
     The method may further include detecting that the motor has stopped generating an excess voltage and, if the circuit path is clamped to the battery, disconnecting the battery from the circuit path when the electric motor has stopped generating the excess voltage. The method may further include detecting that the rotational speed is below a lower rotational speed threshold and, if the circuit path is clamped to the battery, disconnecting the battery from the circuit path when the motor has stopped generating the excess voltage and/or the rotational speed is below the lower rotational speed threshold. 
     In another aspect, the present disclosure provides a device for controlling an electric motor in a vehicle, the vehicle having a circuit path between a battery of the vehicle and the electric motor. The device may include at least one controller in electrical communication with the circuit path, a harness relay disposed in electrical communication with the circuit path and configured to break or complete the circuit path between the electric motor and the controller, and a main relay disposed in electrical communication with the circuit path and configured to break or complete the circuit path between the electric motor and the battery. The controller may be configured to close the harness relay to complete the circuit path between the electric motor and the controller when the electric motor is being back-driven, detect when a voltage generated by back-driving the motor exceeds an upper voltage threshold, detect when a rotational speed generated by back-driving the motor exceeds an upper rotational speed threshold, and, upon detection of the voltage exceeding the upper voltage threshold or the rotational speed exceeding the rotational speed threshold, cause the main relay to close, completing the circuit path from the electric motor to the battery to charge the battery with the voltage. The controller may be further configured to detect whether the controller is powered by the battery and, if the controller is not powered by the battery, maintain the harness relay in an open position to break the circuit path between the electric motor and the controller. The controller may be further configured to detect that the voltage is no longer above the upper voltage threshold, detect that the rotational speed is below a lower rotational speed threshold, and open the main relay when the voltage is below the upper voltage threshold and the rotational speed is below a lower rotational speed threshold. 
     In another aspect, the present disclosure provides a method for preventing thermal damage to an electric motor in a vehicle. The method may include monitoring the motor, detecting a cycle of the motor, and: if the cycle occurred within a predetermined increment time, incrementing a cycle count; if no cycle occurs for a predetermined decrement time, decrementing the cycle count if the cycle count is greater than zero; and, if the cycle count is at least equal to a cycle limit, deactivating power operation of the motor for at least the decrement time. The method may further include detecting an ambient temperature of the vehicle and decreasing the cycle limit if the ambient temperature exceeds one or more ambient temperature thresholds. The method may further include increasing the decrement time if the ambient temperature exceeds one or more of the ambient temperature thresholds. 
     The method may further include continuously calculating energy consumed by the motor as the motor is monitored. If the energy consumed exceeds one or more allowable energy thresholds, the method may include setting the cycle count equal to the cycle limit. Calculating the energy consumed may include measuring and integrating an electrical current consumed by the motor. Calculating the energy consumed may include setting a first limit of integration and a second limit of integration larger than the first limit of integration, setting a first of the allowable energy thresholds as a short period threshold and a second of the allowable energy thresholds as a long period threshold, measuring and integrating, within the first limit of integration, an electrical current consumed by the motor, measuring and integrating the electrical current within the second limit of integration, and, if the energy consumed within the first limit of integration exceeds the short period threshold or the energy consumed within the second limit of integration exceeds the long period threshold, setting the cycle count equal to the cycle count limit. The method may further include detecting an ambient temperature of the vehicle and decreasing one or more of the allowable energy thresholds if the ambient temperature exceeds one or more ambient temperature thresholds. The method may further include detecting a failure condition and setting the cycle count equal to the cycle limit when the failure condition is detected. 
     The method may further include determining the one or more allowable energy thresholds. Determining the one or more allowable energy thresholds may include characterizing a power operation mode and characterizing a manual operation mode. Characterizing the power operation mode may include identifying a worst case condition of operating the motor, monitoring an internal temperature of the motor, operating the motor in the worst case condition until the internal temperature reaches a desired temperature limit, and calculating the energy consumed by the motor for the internal temperature to reach the temperature limit. 
     The method may further include determining the cycle limit. Determining the cycle limit may include monitoring an internal temperature of the motor, operating the motor until the internal temperature reaches a desired temperature limit, and setting the cycle limit to the number of cycles needed for the internal temperature to reach the temperature limit. 
     The cycle may be included in the cycle count both when the cycle is a powered operation and when the cycle is a manual operation. The increment to the cycle count may be multiplied by a multiplier greater or less than 1 if the cycle is a manual operation. The method may further include, if the cycle count is at least equal to a maximum cycle count greater than the cycle limit, deactivating manual operation of the motor at least until the cycle count is less than the cycle limit. 
     In another aspect the present disclosure provides a device for preventing thermal damage to a clutchless electric motor in a vehicle. The device may include an electronic control unit in electrical communication with the motor and configured to monitor operations of the motor, maintain a cycle count and a cycle limit each representing a number of cycles of the motor, increment the cycle count if a cycle is detected within a predetermined increment time, decrement the cycle count if the cycle count is greater than zero and no cycle occurs for a predetermined decrement time, and deactivate power operation of the motor for at least the decrement time if the cycle count is at least equal to the cycle limit. The device may include a non-volatile memory, and the electronic control unit may be further configured to store one or both of the cycle count and the cycle limit in the non-volatile memory, and, if power to the electronic control unit is interrupted, retrieve one or more of the cycle count and the cycle limit from the non-volatile memory when power is restored. The electronic control unit may store the cycle count to memory each time the cycle count is incremented or decremented. The electronic control unit may include a capacitor having sufficient capacitance to allow the electronic control unit to store the cycle count to the non-volatile memory within a buffer time after power to the electronic control unit is interrupted. The electronic control unit may be configured to set the cycle count to the cycle limit when power is restored if the retrieved cycle count exceeds a fixed percentage of the cycle limit. 
     These and still other aspects will be apparent from the description that follows. In the detailed description, preferred example embodiments will be described with reference to the accompanying drawings. These embodiments do not represent the full scope of the concept; rather the concept may be employed in other embodiments. Reference should therefore be made to the claims herein for interpreting the breadth of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is a side plan view of a power tailgate on a vehicle. 
         FIG. 1B  is a diagram of an electric motor control system of the vehicle of  FIG. 1A . 
         FIG. 2  is a chart depicting a voltage generated by mechanically driving the electric motor. 
         FIG. 3  is a flowchart of one embodiment of a method of managing back EMF voltage of the electric motor. 
         FIG. 4  is a timing diagram illustrating an application of the method of  FIG. 3 . 
         FIG. 5  is a chart depicting a correlation between a mechanical driving force and revolutions-per-minute of the electric motor. 
         FIG. 6  is a flowchart of another embodiment of a method of managing back EMF voltage of the electric motor. 
         FIG. 7  is a timing diagram illustrating an application of the method of  FIG. 6 . 
         FIG. 8  is a timing diagram illustrating another application of the method of  FIG. 6 . 
         FIG. 9  is a diagram of an exemplary control circuit for the electric motor. 
         FIG. 10  is a flowchart of another embodiment of a method of managing back EMF voltage of the electric motor. 
         FIGS. 11 and 12  are charts depicting a motor temperature over time in different protective embodiments. 
         FIG. 13  is a flowchart of one embodiment of a method of regulating heat generated by an electric motor. 
         FIG. 14  is a timing diagram illustrating an application of the method of  FIG. 13 . 
         FIG. 15A  is a state diagram of a device for calculating the consumed energy of an electric motor. 
         FIG. 15B  is a timing diagram of a method of calculating the consumed energy of an electric motor. 
         FIG. 15C  is a timing diagram of a method of regulating heat generated by an electric motor based on consumed energy. 
         FIG. 16  is another side plan view of a power tailgate on a vehicle. 
         FIG. 17  is a timing diagram of a method of regulating heat generated by an electric motor based on a failure condition detection. 
         FIG. 18  is a flowchart of another embodiment of a method of regulating heat generated by an electric motor. 
         FIG. 19  is a flowchart of an embodiment of a temperature recovery method for an electric motor. 
         FIG. 20  is a chart depicting the temperatures of several components of an electric motor as the motor is operated over time. 
         FIG. 21  is a timing diagram of a method of regulating heat generated by an electric motor based on powered and manual operations of the motor. 
         FIG. 22  is a timing diagram of another method of regulating heat generated by an electric motor based on powered and manual operations of the motor. 
         FIG. 23  is a timing diagram of another method of regulating heat generated by an electric motor based on powered and manual operations of the motor. 
         FIG. 24  is a timing diagram of a method of writing relevant parameter data to non-volatile memory. 
         FIG. 25  is a timing diagram of another method of writing relevant parameter data to non-volatile memory. 
         FIG. 26  is a flowchart of a method of verifying motor thermal characteristics. 
         FIG. 27  is a plan view of two embodiments of testing worst case conditions of an electric motor operation for a power tailgate. 
         FIGS. 28A-B  are charts depicting increasing and decreasing motor temperature, respectively, in light of determined thresholds in accordance with the method of  FIG. 26 . 
         FIG. 29  is a chart depicting a cooling trend of an electric motor applying the methods of regulating heat of the present disclosure. 
         FIG. 30  is a plan view of an embodiment of verifying temperature increase of an electric motor during manual operations of the motor. 
         FIG. 31  is a plan view of another embodiment of verifying temperature increase of an electric motor during manual operations of the motor. 
     
    
    
     DETAILED DESCRIPTION OF THE EXAMPLE EMBODIMENTS 
     The concepts described below and shown in the accompanying figures are illustrative of example implementations of the inventive concepts; however, when given the benefit of this disclosure, one skilled in the art will appreciate that the inventive concepts described herein can be modified and incorporated into many other applications. Furthermore, throughout the description terms such as front, back, side, top, bottom, up, down, upper, lower, inner, outer, above, below, and the like are used to describe the relative arrangement and/or operation of various components of the example embodiment; none of these relative terms are to be construed as limiting the construction or alternative arrangements that are within the scope of the claims. 
     In particular, the concepts described below for controlling an electric motor and associated control electronics may be suitable for application to any electric motor. Specific arrangements are described below, wherein the motor operates a powered vehicle door between open and closed positions.  FIGS. 1A and 1B  illustrate an example vehicle  102  having a door  101 , which may be a powered tailgate (PTG), operated by an electric motor  111  according to any suitable mechanical arrangement. In the illustrated example mechanical arrangement, the electric motor  111  rotates a pinion  106 , and the rotational motion is transferred to linear motion of a rack  107  that intermeshes with the pinion  106 . The rack  107  in turn moves a pivoting link  108  that is attached to the door  101  and causes the door  101  to swing open or closed around a hinge  103  (see line-of-motion L). A biasing member  104 , such as a gas or hydraulic stay, may hold the door  101  in the open position or in any position between open and closed. 
     The motor  111  may be powered by a vehicle battery  114 , which may be directly connected to the motor  111  in some embodiments, and in other embodiments may be connected to the motor  111  via one or more control circuits. Each control circuit may include a controller  115 , which may be an electronic control unit (ECU) and other control electronics, such as microprocessors, voltage regulators, switches, integrated and non-integrated circuits, transistors, relays, control logic, volatile and non-volatile memory, and other electronic components suitable for performing the control algorithms in accordance with this disclosure. The algorithms are described as being performed by the controller  115 , which is typically present in the circuit, but it will be understood that other electronic components of the control circuit may perform the algorithms. 
     Power Management of Back EMF Generated by an Electric Motor 
     When electrical energy is applied to an electric motor, the motor typically electrically rotates a drive shaft to perform mechanical work. To the contrary, the drive shaft of the motor can be mechanically rotated, which causes the motor to become a generator producing electrical energy known as back electromagnetic force (back EMF). In some arrangements, such as those employed with electrically assisted or powered vehicle doors, hatches, or liftgates (e.g., a PTG), a clutch is typically employed to mechanically decouple the motor from the door during non-powered mechanical movement (e.g., manual opening or closing) of the door. Without a clutch, the motor is continuously coupled to the door and, as generally illustrated in  FIG. 1 , non-powered mechanical movement of the door  101  (along line L) rotates the drive shaft (not shown) of the motor  111  and generates a back EMF voltage (see  FIG. 2 ) that has the potential to damage the controller&#39;s  115  sensitive components and other electronics that are in electrical communication with the motor  111 . 
     In accordance with the present disclosure, several methods and device configurations may be applied separately or in conjunction to address the problems associated with excessive back EMF caused by mechanical rotation of the electric motor  111 .  FIGS. 3 and 4  illustrate a first embodiment of a method performed by the controller  115  to electronically divert dangerously high back EMF voltage to the vehicle battery  114 , thereby charging the battery and preventing the excessive voltage from entering and damaging any electronic components that are in a circuit path with the motor  111 . At step  300 , the controller  115  monitors the voltage generated by mechanically driving the motor  111 . Monitoring the voltage may include detecting, at time T 1 , the back EMF voltage on one or more wires or other conductive lines connected to the motor  111 . In some embodiments, the controller  115  may detect the voltage directly, such as by sensing a voltage on an input port of the controller  115 . In other embodiments, the controller  115  may detect another indicator that the motor is being mechanically driven, such as a signal from a motion sensor or hall effect sensor or from a suitable magnetic or electrical pulse detector. An example is illustrated in  FIG. 4 , wherein the controller  115  detects a pulse switching from a low (LO) to a high (HI) state at time T 1 . 
     At step  305 , the controller  115  may compare the monitored voltage to one or more voltage thresholds. If the controller  115  determines that the voltage is lower than a voltage threshold requiring action to attenuate it, referred to herein as an upper voltage threshold, the controller  115  continues monitoring the voltage. If the controller  115  determines that the voltage meets or exceeds the upper voltage threshold, at step  310  the controller  115  may clamp the circuit path to the battery  114 . Clamping the circuit path may include activating one or more switches, such as a relay (labeled “Main Relay” in  FIG. 4  and described further herein), to electrically connect the battery  114  to the circuit path. The effect is to divert the voltage in excess of the battery  114  voltage to the battery  114 , which has the advantages of preventing excessive voltage on the electronic components, and charging the battery  114  with the excess voltage. The timing diagram of  FIG. 4  illustrates that the controller  115  detects the voltage reaching an upper voltage threshold of 18 volts at time T 2 , at which time the controller  115  activates the relay and the voltage in the circuit path drops to the battery  114  voltage of about 12 volts (see the curve labeled ‘Port1’). Some embodiments may include circuit components, such as one or more capacitors and/or transistors, that allow the voltage to drop gradually to the battery  114  voltage more gradually than that shown in  FIG. 4 . 
     The controller  115  may continue to monitor the voltage as in step  300 , or may continue to detect the pulse or other indicator that the motor  111  is being mechanically driven, at step  315 . As long as the voltage is being generated, the controller  115  may maintain the clamp of the circuit path to the battery  114  (i.e., by keeping the relay activated). When the controller  115  detects that the motor has stopped generating an excess voltage, either by detecting a drop in the voltage or a change in the indicator (e.g., a detected pulse changing from HI to LO), at step  320  the controller  115  may deactivate the relay to unclamp the circuit path from the battery  114 . In some embodiments, the controller  115  may unclamp the circuit path (e.g., at time T 3  of  FIG. 4 ) after a release time R has passed, allowing the voltage to drop to a safe level (e.g., below the battery  114  voltage). 
     In another embodiment of diverting the excess back EMF voltage, the controller  115  may be configured to clamp the circuit path to the battery at a fast rotational motor speed condition when the rotational speed of the motor (e.g., a motor drive shaft coupled to the device) equals or exceeds an upper rotational speed threshold. Referring to  FIG. 5 , the force (illustrated on the vertical axis in units of kilogram-force) with which the motor  111  is be mechanically driven correlates to the rotational speed (illustrated on the horizontal axis in units of revolutions per minute) of the motor. The rotational speed in turn correlates to the generated back EMF voltage; under high rotational speeds, large and potentially damaging voltages are generated. In an example correlative test, the results of which are shown in  FIG. 5 , collected data points (indicated by squares) show a linear correlation of force to RPM. 
       FIGS. 6 and 7  illustrate an embodiment of a method performed by the controller  115  to electronically divert dangerously high back EMF voltage to the vehicle battery  114 , thereby charging the battery and preventing the excessive voltage from entering and damaging any electronic components that are in a circuit path with the motor  111 . At step  600 , the controller  115  monitors the speed of the motor  111  as it is mechanically driven. Monitoring the speed may include detecting, at time T 1 , that the motor  111  shaft, stator, or other component is rotating. In some embodiments, a sensor, such as a hall sensor, may detect the rotation and rate of rotation of the motor  111  and may deliver a signal to the controller  115 , the signal describing the detected characteristics. An example is illustrated in  FIG. 7 , wherein the controller  115  detects that a hall sensor has activated at time T 1 , and the controller  115  receives the speed of the motor  111  from the hall sensor. 
     At step  605 , the controller  115  may compare the monitored speed to one or more speed thresholds. If the controller  115  determines that the speed is lower than a speed threshold requiring action to attenuate the correlated voltage, referred to herein as an upper speed threshold, the controller  115  continues monitoring the speed. If the controller  115  determines that the speed meets or exceeds the upper speed threshold, at step  610  the controller  115  may clamp the circuit path to the battery  114 . Clamping the circuit path may include activating one or more switches, such as a relay (labeled “Main Relay” in  FIG. 7  and described further herein), to electrically connect the battery  114  to the circuit path. The effect is to divert the voltage in excess of the battery  114  voltage to the battery  114 , which has the advantages of preventing excessive voltage on the electronic components, and charging the battery  114  with the excess voltage. The timing diagram of  FIG. 7  illustrates that the controller  115  detects the speed reaching an upper speed threshold at time T 2 , at which time the controller  115  activates the relay and the voltage in the circuit path drops to the battery  114  voltage of about 12 volts. Some embodiments may include circuit components, such as one or more capacitors and/or transistors, that allow the voltage to drop more gradually to the battery  114  voltage than is illustrated in  FIG. 7 . 
     The controller  115  may continue to monitor the speed as in step  600  by processing the data from the hall sensor or other indicator that the motor  111  is being mechanically driven, at step  615 . As long as the speed is above a lower speed threshold, the controller  115  may maintain the clamp of the circuit path to the battery  114  (i.e., by keeping the relay activated). When the controller  115  detects that the motor has stopped or mostly stopped rotating, such as when the hall sensor deactivates or the lower speed threshold is reached, at step  620  the controller  115  may deactivate the relay to unclamp the circuit path from the battery  114 . In some embodiments, the controller  115  may unclamp the circuit path (e.g., at time T 3  of  FIG. 7 ) after a release time R (of about 500 ms) has passed, allowing the voltage to drop to a level below the battery  114  voltage). 
       FIG. 8  illustrates another embodiment of clamping the circuit path to the battery  114  as in  FIG. 6 . According to the illustrated timing diagram, the controller  115  may first detect that the motor  111  is being manually or otherwise mechanically driven, at time T 1 . At this time, the controller  115  may initiate a pre-charge of one or more capacitors in the circuit path, which has the advantage of minimizing stress on electronic components in a high-voltage situation when the back EMF voltage or battery  114  voltage is introduced into the circuit path. The pre-charge period P may be a suitable duration, such as 150 ms, to ensure that each capacitor is fully charged before any high-voltage relay is activated. The controller  115  then detects, at time T 2 , the speed equaling or exceeding the upper speed threshold. In the illustrated embodiment, the controller  115  then activates two relays in sequence: first, the controller  115  activates the main relay connecting the battery  114  to the circuit path as described above; then, after a stabilizing period S of between zero and about 20 ms, the controller  115  may activate a second relay (labeled “Harness Relay”) electrically connecting the motor  111  to the circuit path. Alternatively, the second relay may be activated before the main relay. When both relays are activated, the circuit path is clamped to the battery  114  and transfers back EMF voltage that exceeds the battery  114  voltage to the battery  114 . The controller  115  may maintain the clamping until the speed is at the lower speed threshold (see time T 3 ′), at which time the controller  115  may deactivate one or both relays immediately or after a release time R has passed. 
       FIG. 9  illustrates an embodiment of a control circuit configured to perform the above-described methods of managing motor  111  back EMF. The control circuit includes the controller  115  electrically connected to the motor  111  and a harness relay  120  of the vehicle  102  via power lines  130 ,  132 . The controller  115  may include a microprocessor  150  that may be connected to one or more integrated circuits (ICs) for controlling the operation of the motor  111 , the harness relay  120 , and a main relay  140  that electrically connects the control circuit and motor  111  to the battery  114  when the main relay  140  is activated. It will be understood that the ICs that are electrically connected to the microprocessor  150  may alternatively be external to the controller  115  and/or be replaced or substituted with equivalent discrete components where necessary or advantageous for the application. 
     The ICs may include an H-bridge  158  and an H-bridge driver  152 , one or more speed control circuits  160 , and one or more communication circuits  162 . The H-bridge  158  provides a two-way voltage path between the motor  111  and the battery  114 , which powers the motor  111  during powered operations of the motor  111 . The H-bridge  158  may be any suitable H-bridge IC, such as a four-gate IC wherein the gates are field-effect transistors (FETs). The H-bridge driver  152  may operate the gates of the H-bridge  158  with a gate driver  156  as is known in the art. The gate driver  156  may receive gate switching sequence commands from stored control logic  154  that converts operating commands from the microprocessor  150  or stored automated commands into switching sequences for the H-bridge  158  gates, which in turn determines how power is applied to the motor  111  (i.e. rotation direction, force magnitude, and duration via pulse width modulation or other known techniques). The microprocessor  150  commands may additionally be processed by the speed control circuits  160  and/or the communication circuits  162  before they are transmitted to the control logic IC  154 . 
     Some or all of the components of the controller  115  may receive an input voltage within the control circuit. In the illustrated example control circuit, at least the microprocessor  150  (via “Port 1”) and the gate driver  156  (see voltage V S ) receive the input voltage. The input voltage may be provided by the battery  114  when the main relay  140  is activated (i.e., closed) and/or the motor  111  is not being mechanically driven. When the motor  111  is being mechanically driven, however, the motor  111  may generate a back EMF voltage that appears at port 1, and, subsequently, the input voltage of the control circuit. Additional power supplies, such as system backup power (VBU) or onboard batteries (e.g., providing voltage V CC  to the control logic  154 ) may power other components of the system. 
     The microprocessor  150 , control logic  154 , or another component of the controller  115  may store instructions for performing methods of managing back EMF by monitoring the back EMF voltage, the motor  111  rotational speed, or both. To monitor voltage as described above with reference to  FIG. 3 , the controller  115  may detect that the motor  111  is rotating via a current or voltage on a first power line  130  and may close the harness relay  120  in reaction to the detected rotation. Then, the controller  115  may monitor the back EMF voltage across the power lines  130 ,  132  (e.g., via inputs to the microprocessor  150  at “Port 2” and “Port 3”). The controller  115  may put the H-bridge  158  in a state that allows the current induced by the rotation to flow into the controller  115  (e.g., at Port 1 and V S ). The controller  115  may continuously or periodically compare the voltage to the upper voltage threshold. When the upper voltage threshold is met by the voltage, the controller  115  may close the main relay  140  to alleviate the excess voltage. As described above, the voltage (e.g., V S ) then drops to the battery  114  voltage, the excess current flowing into and charging the battery  114 . 
     To monitor speed as described above with reference to  FIG. 6 , the controller  115  may communicate with a sensor  170  configured to detect the rotational speed of the motor  111  and report it to the controller  115 . The sensor  170  may be electrically connected to the control circuit, such as on the second power line  132  as illustrated, or may be electrically isolated from the circuit. A suitable type of sensor  170  may depend on whether the sensor  170  is connected to or isolated from the circuit path. In some embodiments, the sensor  170  is a hall effect sensor that senses changes in a magnetic field of the motor  111  to determine the rotational speed. The controller  115  may close the harness relay  120  and put the H-bridge  158  in a state that allows the current induced by the rotation to flow into the controller  115  (e.g., at Port 1 and V S ) in reaction to the detected rotation. Alternatively, the controller  115  may leave the harness relay  120  open until an excess rotational speed is detected. The controller  115  may monitor the rotational speed as reported by the sensor  170  and may continuously or periodically compare the rotational speed to the upper rotational speed threshold. When the upper rotational speed threshold is met by the rotational speed, the controller  115  may close the main relay  140  (and the harness relay  120  if it is still open) to alleviate the excess voltage. As described above, the voltage (e.g., V S ) then drops to the battery  114  voltage, the excess current flowing into and charging the battery  114 . 
     In addition or alternatively to the above methods of managing back EMF of the motor  111 , a protection method for instances when the controller  115  is not powered may be applied. Such an instance may arise when, for example, the battery  114  is completely disconnected from the vehicle  102 . The protection method may include breaking the circuit path to prevent the flow of excessive current into the unpowered controller  115  or H-bridge driver  152 . Breaking the circuit path may involve leaving the harness relay  120  open while the battery is disconnected. 
     These methods and devices manage the power generated by mechanical rotation of the electric motor in an automotive application. The methods may be combined to provide a multifaceted management and protection scheme. The methods may be used independently to provide protection to the electrical systems of the vehicle, or can be used in conjunction with one another to provide overlapping protection and redundancy. In some embodiments, the methods may be performed in parallel. For example, the controller  115  may monitor both the back EMF voltage (as in step  300  of  FIG. 3 ) and the motor  111  speed (as in step  600  of  FIG. 6 ), contemporaneously compare the monitored values to their respective thresholds, and clamp the circuit path to the battery  114  in an excess condition. In other embodiments, the methods may be performed in sequence. In one embodiment, illustrated in  FIG. 10 , at step  1000  if the controller  115  is unpowered, the harness relay  120  remains open and current generated by the motor  111  cannot enter the controller  115 . If the controller  115  is powered, at step  1005  the controller  115  detects that the motor  111  is rotating. Detection may be by any suitable means, including sensing a voltage on one of the power lines  130 ,  132 , sensing movement of the motor  111 , receiving sensor data indicating that the motor  111  is rotating, and the like. At step  1010 , the controller  115  may close the harness relay  120  and, at step  1015 , begin monitoring the motor speed as described above. At step  1020  the controller  115  may compare the monitored rotational speed to the upper rotational speed threshold. If the rotational speed exceeds the threshold, the controller  115  may clamp the circuit path to the battery  114  at step  1035 . 
     If the rotational speed is below the upper rotational speed threshold, at step  1025  the controller  115  may obtain the value of the back EMF voltage as described above. At step  1030 , the controller  115  may compare the voltage to the upper voltage threshold, and may clamp the circuit path to the battery  114  (i.e., by closing the main relay  140 ) at step  1035  if the threshold is exceeded. If the upper voltage threshold is not exceeded, the controller  115  may return to monitoring the speed (as illustrated) or the voltage. Once the circuit path is clamped to the battery  114 , the controller  115  may continuously or periodically check both the motor  111  rotational speed (at step  1040 ) and the back EMF voltage (at step  1045 ) to see if both have returned to a safe level. At step  1050 , the controller  115  may release the clamp, after the release time R in some embodiments, when safe levels of speed and voltage are reported. 
     Regulation of Heat Generated by an Electric Motor 
     Controlling the amount of heat generated by an electric motor during use is a consideration in many applications, such as powered door, hatch, and liftgate automotive applications. Typically, physical components are used to temporarily deactivate the motor to allow it to cool. Due to reduced packaging constraints, the space available for electric motors used in automotive applications has decreased. In order to produce increasingly compact electric motors, one component that may be eliminated in certain applications is a positive-temperature-coefficient (PTC) thermal breaker. With reference to  FIG. 11 , the thermal breaker is typically configured to heat up and ultimately block current flow to the motor  111  at some temperature  205  below the motor damage threshold  200 , thus preventing current flow runaway that could potentially damage the electric motor  111  and associated electronics. Unfortunately, in addition to the disadvantages of PTC thermal breakers described above, the breaker can be tripped at any time during operation of the motor  111 , resulting in sudden and unannounced operational halts that can cause damage and injury. However, without a thermal breaker, the heat generated by the electric motor  111  goes unchecked and can have detrimental impacts on the electric motor and associated components. 
     To address these heat generation issues, the amount of heat generated in an electric motor can be regulated by the electronic controller  115  (e.g., via a software implementation), eliminating components within the motor  111 . For example, and with initial reference to  FIG. 12 , cycle limitation (the number of motor  111  cycles permissible is regulated), energy consumption limitation (the current consumed by the motor  111 , which is proportional to the temperature of the motor  111 , is measured and integrated), and failure mode limitation (detection of abnormally high loads or operational failure) methods can be employed to regulate the amount of heat generated in the motor  111  before the motor  111  may be temporarily deactivated to allow the temperature of the motor to decrease. 
     These methods can be applied individually, and further may be applied in conjunction with each other to form an even more robust approach to managing heat generation. For instance, the energy consumption limitation method may supplement the cycle limitation method to account for factors such as the ambient temperature or increased loads on the motor  111  (e.g., when a powered liftgate is being operated at an incline). These concepts allow for smaller packaging and the ability to predict when an overheat and/or termination condition will arise, reducing incidents of unexpected terminations occurring without warning in PTC-based overheat protection systems. 
     The cycle limitation method involves regulating the permissible number of cycles, each cycle being a complete operation of the motor  111 . For example, when a user presses a button on a key fob, causing the PTG to open, a cycle is the operation of moving the PTG from a fully closed state to a fully open state. Referring to  FIGS. 13 and 14 , the controller  115  may perform an embodiment of the cycle limitation method by tracking the number of cycles of the motor  111 . The controller  115  may monitor the operations of the motor  111 , at step  1300 , waiting for a cycle to occur. At step  1305 , the controller detects a cycle. The controller  115  may use any suitable method to determine that a cycle (i.e., a complete PTG operation) has occurred. For example, according to the timing diagram of  FIG. 14 , the controller  115  may measure the duration of a pulse correlating to the powered operation. The value of a pulse (e.g., the first pulse  1400 ) on the pulse graph  1405  increases linearly with time and indicates a cycle when it reaches the maximum pulse value  1410  (correlating to the distance of one complete operation). 
     The controller  115  may store or otherwise retain a predetermined increment time T i , a predetermined decrement time T c , a predetermined numerical cycle limit C L , and a variable cycle count C C . The values of T i , T c , and C L  may be selected to reflect the heating and cooling characteristics of the motor  111 . That is, the increment time T i  may be approximately the duration that the motor  111  must remain idle after a cycle for the motor  111  to cool to its pre-cycle temperature (i.e., the temperature of the motor  111  before the cycle occurred). The decrement time T c  may be approximately the duration that the motor  111  must remain idle after a cycle for the motor  111  to cool to its temperature of before the previous two cycles. The cycle limit may be the maximum number of substantially contemporaneous cycles (i.e., a cycle occurs within the increment time T i  after the previous cycle) that the motor  111  can tolerate before its temperature becomes dangerously high. Each of the increment time T i , decrement time Tc, and cycle limit C L  may be affected by the ambient temperature surrounding the motor  111 , which value may be transmitted to the controller  115  by a temperature sensor. In particular, higher ambient temperatures may increase the decrement time Tc and decrease the cycle limit C L  because the motor  111  takes longer to cool in such temperatures. TABLE 1 is a table of example values for T i , T c , and C L  in different ambient temperature ranges, where time durations are measured in seconds. 
     
       
         
           
               
               
               
               
               
             
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                 TEMP (Deg C.) 
                 C L   
                 T i   
                 T c   
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
            
               
                   
                 Below 35 
                 20 
                 30 
                 60 
               
               
                   
                 Btwn 35 and 50 
                 15 
                 30 
                 80 
               
               
                   
                 Above 50 
                 10 
                 30 
                 120 
               
               
                   
                   
               
            
           
         
       
     
     When the controller  115  detects the cycle, the controller checks the time elapsed t since the most recent previous cycle was detected and compares the time elapsed t to the increment time T i , at step  1310 . If the time elapsed t is less than or equal to the increment time T i , at step  315  the controller  115  increments the value of the cycle count C C .  FIG. 4A  illustrates an example, where a second operation  1421  follows a first operation  1420  by a time t that is less than the increment time T i . The cycle count graph  1415  shows the cycle count C c  being incremented by one when the second pulse  1401  reaches the maximum pulse value  1410 . In contrast, if the time elapsed t since the previous cycle is greater than the increment time T i , the cycle is not counted in the cycle count C C  and the controller  115  returns to monitoring the motor operations (step  300 ). For example, the third operation  1422  and fourth operation  1423  occur after the increment time T i  has passed since the previous operation and the cycle count C C  is not incremented. 
     When the cycle count C C  is incremented at step  1315 , the controller  1315  may then compare the value of the cycle count C C  to the cycle limit C L . If the cycle limit C L  has been reached or exceeded, at step  1325  the controller  115  may enter a temperature recovery mode, wherein one or more functions of the PTG (or other device being driven by the motor  111 ) may be temporarily disabled as described below to allow the motor  111  to cool. It will be understood that the controller  115  may perform this comparison at another point in the described method, such as immediately before or after detecting the cycle, which may cause the controller  115  to enter the temperature recovery mode earlier or later as needed. 
     While the controller  115  is monitoring the motor operations and a cycle is not detected, the controller  115  may compare the elapsed time t since the last cycle to the decrement timer Tc, at step  1330 . When the elapsed time t meets or exceeds the decrement timer Tc, at step  1335  the controller  115  may decrement the cycle count C C  if the cycle count is greater than zero. An example is illustrated in  FIG. 14 , where the cycle count C C  is decremented gradually to zero as the decrement time Tc passes repeatedly with no cycles detected after a last operation  1425 . 
     In some applications, the cycle limitation method may not be sufficiently accurate or responsive due to it counting complete operations of the motor. For example, partial operations, increased loads on the motor  111 , and other conditions can contribute to the motor  111  temperature but are not directly added to the cycle count. An energy consumption limitation method may be used alternatively or complementarily to the cycle limitation method to account for motor  111  operation that may not be tracked by the cycle count limitation method. The energy consumption limitation method involves measuring and integrating the current consumed by the motor  111 ; this value is approximately proportional to the heat generated by and the temperature of the motor  111 . The calculated energy figures can be compared to threshold values stored in a lookup table. When the threshold is exceeded, operation of the motor may be disabled. 
       FIGS. 15A-B  illustrate calculation of the energy consumed by the motor  111 . Referring to  FIG. 15A , the energy U may be calculated with the equation:
 
 U=∫Pdt  
 
where P is the power (wattage) applied by the motor  111  and may be obtained for any instant of time by multiplying the motor current by the motor power voltage and scaling by the motor drive duty, if any. This value is integrated at each unit of time within the limits of integration and summed with the previous calculated value to find the energy U consumed as of that time. The limits of integration may define a suitable time period across which the power is integrated.  FIG. 15B  illustrates a power graph  1500  and an energy graph  1550  showing the calculated power applied  1505  and energy consumed  1555 , respectively, by the motor  111  across the same time interval. The motor  111  is performing a powered operation from time T ON  to time T OFF . The amount of power applied is integrated over a continuously updated time in an integration window  1510  having limits of integration W. The calculated integration values, representative of the instantaneous energy consumed, are summed as the integration window  1510  moves across the period of powered operation. Thus, as the integration window  1510  enters and covers the power  1505  area, the energy  1555  increases until an energy saturation point, when the integration window  1510  is fully within the power  1505 , at time T SAT . The calculated energy  1555  plateaus while the integration window  1510  is saturated, until the powered operation is stopped at time T OFF . Calculation of the consumed energy U may continue, decreasing until the integration window  1510  fully exits the power  1505  area at time T OUT .
 
     The controller  115  may track the consumed energy U and compare it to one or more energy thresholds  1560 . The energy thresholds  1560  may be stored, such as in a lookup table, by the controller  115 . In some embodiments, when the consumed energy U exceeds the energy threshold  1560 , the controller  115  may disable one or more operations of the motor  111  according to the temperature recovery mode described herein. Referring to  FIG. 15C , in some embodiments the energy consumption limitation may be used in conjunction with the cycle count limitation. In the illustrated example, when the calculated consumed energy U exceeds an energy limit E L  (which may correspond to the energy threshold  1560  of  FIG. 15B ) at time T L , the controller  115  sets the cycle count C C  to the cycle limit C L  to invoke the temperature recovery mode. The cycle count decrement process may also be augmented by providing an energy decrement time T E  that must elapse after a powered operation is terminated before the cycle count C C  may be decremented. In other embodiments, the controller  115  may merely increment the cycle count C C  as normal when the energy limit E L  is exceeded. 
     In still other embodiments, the controller  115  may use a plurality of integration windows  1510 , setting a first limit of integration for a first window  1510  and a second limit of integration larger than the first limit of integration for the second window  1510 , to provide for monitoring different levels and periods of consumption. For example, one setting may protect for short periods of high energy consumption, while the second setting may protect for long periods of prolonged energy consumption. Correspondingly, a plurality of energy thresholds  1560  may be set to accommodate the monitoring goals of the different integration windows. 
     The failure mode limitation method considers when abnormally high loads are applied or if a failure condition has occurred that increases the load. While such conditions could be detected by the energy consumption limitation method, tuning the consumed energy limits of integration to accommodate these conditions applies performance constraints to the system that could be better managed if the failure condition were addressed separately. Specifically, if a failure condition is detected, the cycle limit may be set to the maximum value and the motor disabled. 
       FIG. 16  illustrates an example failure condition, known as “open stay failure,” for which the controller  115  may be configured to protect the motor  111 . An open stay failure occurs when a device that is configured to hold the PTG open, such as the biasing member  104 , fails to do so. For PTGs and other doors, if open stay fails, the PTG can open under high load but will drop under its own weight. The high load open operation may generate large amounts of heat. The controller  115  may be configured to detect the open stay failure. In one embodiment, the controller  115  may count a predetermined number, such as ten, of rapidly occurring open and/or close operations. In another embodiment, illustrated in  FIG. 17 , the controller  115  may detect one or more drops  1700  indicating that the PTG has failed to stay open. At a threshold number of repeated drops  1700  (two sequential drops  1700  from the “Full Open” PTG position in the illustrated embodiment), the controller  115  may perform the close operation to secure the PTG in a closed position, and may set the cycle count CC to the cycle limit CL to incite entry into the temperature recovery mode. The cycle count decrement process may also be augmented by providing a failure decrement time T D  that must elapse after a failure is detected before the cycle count C C  may be decremented. 
     As described above, the cycle limitation, energy consumption limitation, and failure mode limitation methods may be applied together to provide a robust electronically-controlled motor  111  operation management system for maintaining the temperature of and heat produced by the motor  111  below a damaging level. Several methods of combining the methods are described above. Referring to  FIG. 18 , the controller  115  may evaluate the result of the different methods to determine whether to operate the motor  111  normally or enter the temperature recovery mode. The thermal limit of the motor  111  is reached by detection of excessive operation cycles, high energy consumption, or failure mode limitation (e.g., open stay failure detection). In one embodiment, when a thermal function  1800 , such as a powered operation of the PTG, is underway, the controller  115  checks whether a failure limit has occurred at step  1805 . If not, the controller  115  checks whether energy consumption of the motor  111  has exceeded its limit at step  1810 . If not, the controller  115  checks whether the cycle count has exceeded its limit at step  1815 . If not, the controller  115  proceeds with normal operation  1820  of the motor  111 . If any of the queries of steps  1805 ,  1810 , or  1815  are answered in the affirmative, the controller  115  may enter the temperature recovery mode  1825  of operating the motor  111 . 
     While previously existing technology provides no advance warning prior to deactivation of the motor and thus operation, the current concept allows the operation to be completed before operation is restricted to allow the system to cool, without power interruption and with continuous system control. Thus, when the thermal limit has been reached, the controller  115  may enter a temperature recovery mode in which several protective measures may be taken. The current open or close operation of the PTG may be completed, and a notification alarm may sound (e.g., continuously) until the current operation is completed. Commands from input devices, such as a key fob, door switch, or seat switch, may be prohibited. Manual operation of a PTG or other door handle may interrupt the current operation. If there is no open stay failure, the controller  115  may reverse direction of the PTG if a pinching or obstacle in the door path is detected. However, if there is an open stay failure, such a detection may stop the operation of the PTG. Once the operation is completed or terminated by other input, the controller  115  may deactivate power to the motor. TABLE 2 illustrates an example group of operations in the temperature recovery mode. 
     
       
         
           
               
               
               
               
               
             
               
                 TABLE 2 
               
               
                   
               
               
                   
                 Obstacle 
                 Outer 
                 Switch/ 
                   
               
               
                 Situation 
                 Detection 
                 Handle Input 
                 Fob Input 
                 Buzzer 
               
               
                   
               
             
            
               
                 Cycle Limit 
                 Reverse 
                 Power OFF 
                 Ignore 
                 Continuous 
               
               
                   
                 Direction 
                   
                   
                 Alarm 
               
               
                   
                 (3x MAX) 
               
               
                 Energy 
                 Reverse 
                 Power OFF 
                 Ignore 
                 Continuous 
               
               
                 Consumption 
                 Direction 
                   
                   
                 Alarm 
               
               
                 Limit 
                 (3x MAX) 
               
               
                 Failure 
                 Power OFF 
                 Power OFF 
                 Ignore 
                 Continuous 
               
               
                 Mode Limit 
                   
                   
                   
                 Alarm 
               
               
                 Drop 
                 Power OFF 
                 Power OFF 
                 Ignore 
                 Continuous 
               
               
                 Detection 
                   
                   
                   
                 Alarm 
               
               
                   
               
            
           
         
       
     
       FIG. 19  illustrates an example embodiment of the temperature recovery mode  1825 . Upon entry into the temperature recovery mode  1825 , at step  1900  the controller  115  determines if the PTG is operating. If so, at step  1905  the controller  115  may sound the continuous alarm to the PTG user. The controller  115  allows the operation to complete as described above. During the operation, if the controller  115  detects an input from an outer handle of the PTG (at step  1910 , indicating the handle is being actuated by the user), the controller may terminate the operation (step  1915 ). At step  1920 , if the controller  115  detects a seat switch or key fob input, the controller  115  ignores the input. At step  1925 , if the controller  115  detects a pinching or another obstacle in the path of the PTG, and there is no open stay failure, the controller  115  may reverse the direction of the PTG at step  1930 . The controller  115  may reverse the direction up to three times if obstacles are detected. If there is an open stay failure when pinching is detected, the controller  115  may terminate the operation at step  1935 . If no pinching is detected, the controller  115  may finish the operation (step  1940 ). 
     If the controller  115  determines that the PTG is not operating, at step  1955  the controller  115  may attempt an intermediate recovery of the motor  111  to normal operating parameters. An intermediate recovery is a recovery of the normal operating parameters before the full recovery period has elapsed. If the controller  115  determines that an intermediate recovery is permissible, at step  1960  the controller  115  determines whether a predetermined intermediate recovery time has elapsed since the PTG completed its operation. If the controller  115  determines at step  1955  that intermediate recovery is not permissible, the controller  115  checks whether the full recovery time has elapsed since the PTG completed its operation. If the inquiry at steps  1960  or  1965  is answered in the affirmative, at step  1970  the controller  115  may resume normal operation of the motor  111 . If the inquiry at steps  1960  or  1965  is answered in the negative, at step  1980  the controller  115  may receive an outer input from the door handle and determine whether the PTG is in a fully closed or ajar (but not fully open) position. If so, at step  1985  the controller  115  may permit manual release of the PTG but if not, at step  1990  the controller  115  may prohibit the handle operation. 
     Tracking Manual Operation for Motor Thermal Protection 
     When a permanent magnet DC motor is being mechanically driven, the DC motor acts as a generator (see above description related to the generation of back EMF). The generated voltage can create heat within the motor that, if excessive, can result in the degradation or failure of the motor.  FIG. 20  illustrates temperature curves for three components of the motor  111  as the motor  111  is manually (i.e., mechanically) operated 70 times: a rear bearing  2000 ; a brush  2005 ; and a front bearing  2010 . The ambient temperature curve  2015  is also shown. Electronic control algorithms as described above may advantageously account for the manual operations of the motor  111  in calculating the temperature of the motor  111 . 
     The described method includes an algorithm to manage the heat generated due to manual operation of an electric motor, such as by manually moving a powered door/hatch/PTG system. Once the thermal limit threshold is reached, manual operation is permitted and electrically powered operation is prohibited. The maximum number of possible cycles is specified to prevent extended and unnecessary deactivation. Also, even once the thermal limit associated with the electrically powered mode of motor operation is reached, the ability to track and include the mechanical operation in the calculation of an estimated overall motor heat allows manual operation even without any clutch mechanism. Generally, both manual operation and electrical operation of the motor may be deactivated or suspended to provide a sufficient margin against motor damage. 
     In some embodiments, the manual operations may be counted just as powered operations are counted, and may be added to the cycle count C C  that tracks the motor  111  temperature.  FIG. 21  illustrates an embodiment of the manual tracking method that provides extended protection by increasing the recovery time for powered operations. The manual operation at the thermal limit incorporates an extended duration wait because the cycle count C C  is increased a set amount above the cycle limit C L , which extends the duration of the cycle decrement process. An extended cycle limit C E  is maintained by the controller  115 . The extended cycle limit C E  may be a predetermined number of cycles above the cycle limit C L . The controller  115  may count manual open and close cycles using any of the methods described above. When the cycle count C C  reaches the cycle limit C L , powered operation of the PTG may be limited as described above, but the controller  115  may allow manual operations to continue. The controller  115  may continue counting and allowing manual operations in the cycle count C C  above the cycle limit C L , until the extended cycle limit C E  is reached. When the cycle count C C  reaches the extended cycle limit C E , the controller  115  may prohibit manual operations as well as powered operations until the cycle count C C  decrements, as described above, to a safe level (i.e., below the cycle limit C L ). Alternatively, when the cycle count C C  falls below the extended cycle limit C E , manual operations may once again be allowed, while powered operations are prohibited. When the cycle count C C  falls below the cycle limit C L , both powered and manual operations will be allowed. 
       FIG. 22  illustrates an embodiment of the manual operation tracking method that provides improved performance but reduced protection compared to the embodiment of  FIG. 21  by reducing the recovery time for powered operations. The manual operation at the thermal limit does not have an increased duration because the cycle count is not increased a set amount once the cycle limit is reached. Therefore, the decrement timer must perform fewer cycles to reduce the cumulative cycle count. In this embodiment, the controller  115  may increment the cycle count C C  with powered or manual operations as above, but when the cycle limit C L  is reached, the controller  115  may disable both powered and manual operations of the motor  111 . The controller  115  may decrement the cycle count C C  as described above to restore normal operations of the motor  111 . 
       FIG. 23  illustrates another embodiment of the manual operation tracking method, wherein the manual operations may be counted at some multiple R1 that is greater or less than one, so that the manual operations weigh more or less than the powered operations within a pulse count P C . The pulse count P C  may be added to the cycle count C C  of the electrically powered operations of the motor  111  or may replace the cycle count C C , such that the controller  115  tracks motor  111  electrical pulses instead of cycles up to the cycle limit C L . The value of the pulse count P C  may be an integer or a non-integer. For example,  FIG. 23  illustrates a timing diagram in which a powered operation  2305  increases the pulse count P C  by one unit, and a manual operation  2310  increases the pulse count P C  by R1, which is some constant less than one. Thus, in the illustrated embodiment the manual operation has less weight than the powered operation in the pulse count P C . 
     Motor Thermal Protection After Data Interruption 
     When an electronic controller  115  is used to implement a method of thermal protection for an electric motor  111 , problems can arise if the relevant thermal data is corrupted, not retained during a power loss event (e.g., battery  114  disconnect resulting in clearing the memory of the controller  115  or other memory storage device), or the controller  115  is otherwise not able to track the electric motor  111  performance and parameters necessary for thermal management. If the electric motor  111  is nearing a thermal limit (e.g., the cycle limit C L ) and the power cycles, thus erasing the historical thermal data, the motor  111  may be damaged with further use once the power is reapplied. 
     In order to overcome the problems associated with data loss, a method is provided to store in non-volatile memory the relevant data parameters that are used to identify or correlate the temperature of the electric motor  111 . The relevant data parameters may include, without limitation, the cycle count CC, the pulse count PC, any calculated energy consumption values, any detected failure conditions, and any other parameter having a value that may contribute to retrieve the motor  111  state when power is reapplied. In one embodiment, illustrated in  FIG. 24 , the controller  115  may write the cycle count C C  and other relevant parameters to the non-volatile memory  2400  each time a change in the in the cycle count C C  occurs. In another embodiment, illustrated in  FIG. 25 , the controller  115  may monitor its power supply and may store or update the data values in non-volatile memory  2400  when the monitored voltage  2500  indicates a power drop (e.g., at time T P ). The hardware of the controller can be designed to have sufficient capacitance to provide a buffer time (e.g., between time T P  and time T B ) after the power drop during which the supplied voltage  2505  exceeds a minimum operating voltage V M . During the buffer time, the controller  115  has sufficient power to write the data even after the power drop is initially detected. 
     The method may further provide logic to incorporate the historical data into a method of thermal management and protection. Once the controller  115  is operational, the stored data can be used to load the initial conditions relevant to the thermal protection method, which may depend on the type and value of the stored/retrieved data. In one embodiment, the data includes the stored cycle count, which is used to set the current cycle count based on logic and/or a tabulated scheme. In particular, according to TABLE 3, if the loaded value is greater than a fixed percentage of the maximum value in the worst case condition then the cycle limit is set to maximum cycle limit at the high temperature condition. Otherwise, the previous cycle count value is loaded. In an alternative method, the data is set to the maximum or most conservative values to prevent thermal damage to the motor. 
     
       
         
           
               
               
               
             
               
                 TABLE 3 
               
             
            
               
                   
               
               
                 Operation 
                 Operation 
                   
               
               
                 count before 
                 count after 
                 WAIT TIME AFTER RESET 
               
            
           
           
               
               
               
               
               
            
               
                 Reset 
                 Reset 
                 T &lt; 35° C. 
                 35 &lt;= T &lt; 50° C. 
                 50° C. &lt;= T 
               
               
                   
               
            
           
           
               
               
               
               
               
            
               
                 0 
                 0 
                 0 
                 0 
                 0 
               
               
                 1 
                 1 
                 0 
                 0 
                 0 
               
               
                 2 
                 2 
                 0 
                 0 
                 0 
               
               
                 3 
                 3 
                 0 
                 0 
                 0 
               
               
                 4 
                 4 
                 0 
                 0 
                 0 
               
               
                 5 
                 10 
                 0 
                 0 
                 120 s 
               
               
                 6 
                 10 
                 0 
                 0 
                 120 s 
               
               
                 7 
                 10 
                 0 
                 0 
                 120 s 
               
               
                 8 
                 10 
                 0 
                 0 
                 120 s 
               
               
                 9 
                 10 
                 0 
                 0 
                 120 s 
               
               
                 10 
                 10 
                 0 
                 0 
                 120 s 
               
               
                 11 
                 11 
                 0 
                 0 
                 240 s 
               
               
                 12 
                 12 
                 0 
                 0 
                 360 s 
               
               
                 13 
                 13 
                 0 
                 0 
                 480 s 
               
               
                 14 
                 14 
                 0 
                 0 
                 600 s 
               
               
                 15 
                 15 
                 0 
                  80 s 
                 720 s 
               
               
                 16 
                 16 
                 0 
                 160 s 
                 840 s 
               
               
                 17 
                 17 
                 0 
                 240 s 
                 960 s 
               
               
                 18 
                 18 
                 0 
                 320 s 
                 1080 s  
               
               
                 19 
                 19 
                 0 
                 400 s 
                 1200 s  
               
               
                 20 
                 20 
                 60 s 
                 480 s 
                 1320 s  
               
               
                   
               
            
           
         
       
     
     Determination of Thermal Protection Characteristics 
     When thermal protection functions of an electric motor are controlled by software, it can be beneficial to verify that the thermal protection functions will adequately protect the system from overheating in a variety of scenarios. In general, software may be used to predict the thermal condition of the electric motor by using input and output values of the electric motor that are correlated to the amount of heat within the motor. However, without adequate measurement, the appropriate correlation factor is challenging to determine and the parameters that characterize motor thermal characteristics may not be sufficiently accurate over a range of operation. 
     In one approach, the internal temperature of the electric motor is measured and the control values are set based on the target system performance. Benefits of this approach include actual installed condition verification of the software, which allows for enhanced modeling and control of the overall system. A flowchart summarizing an example verification method is described in  FIG. 26  and includes monitoring the temperature of the motor during worst-case operating conditions, calculating the energy consumed to reach an upper temperature limit, and then analyzing and verifying the results and settings. The verification method may characterize the motor  111  under powered operations, wherein heat is generated from the transfer of power from electrical to mechanical form, and under manual operation, wherein heat is generated from the transfer of power from mechanical to electrical form. The procedure can be repeated at various ambient temperatures to enhance the results obtained. The controller  115  or another computer or set of computers may record, analyze, compile, transmit, or otherwise process the data collected by any verification method described herein. 
     To characterize the powered operations of the motor  111 , the motor  111  and the part it drives (e.g., PTG  102 ) may be fitted with thermocouples or other suitable temperature sensors at step  2605 . At step  2610 , one or more tests may then be performed by applying loading conditions to the PTG  102  while performing powered operations of the motor  111 . During or after the tests, at step  2615  the worst case performance conditions may be identified. See  FIG. 27  for example worst case testing conditions (thermal chamber testing at an angle θ incline condition  2705 ; heavy snow load condition  2710 ). Then, at step  2620 , the motor  111  may be operated, such as by continuous cycling of powered operations, until its temperature limit is reached. For testing the worst case conditions, the motor  111  may be operated at maximum torque and/or maximum rated voltage. At step  2625 , the energy consumed to reach the temperature limit may be calculated. At step  2630 , based on the measured operations and calculated consumed energy, one or more cycle thresholds (e.g., cycle limit C L ) and/or one or more energy thresholds (e.g., energy limit E L ) may be set. 
     Once the threshold values are obtained, at step  2635  the obtained values may be tested by again operating the motor  111  to determine whether the thresholds prevent overheating of the motor  111 . If not, the tests may be re-executed by returning to step  2620 . If so, at step  2640  the wait times (e.g., increment time T i  and decrement time T d ) may be obtained, such as by trial and error testing.  FIGS. 28A and 28B  are example graphs of the cycle limit and recovery time setting curves, respectively. Once the wait times are verified as indicating a cooling trend of the motor  111  (step  2645 , see  FIG. 29 ), the powered operations are characterized. 
     To characterize the manual operations of the motor  111 , before or after characterizing the powered operations, the temperature rise of the motor  111  due to manual operations may be verified at step  2650 . One method of testing the temperature rise is illustrated in  FIG. 30 , wherein a first weight M1 is attached to the PTG by a rope and pulley to pull open the PTG. At the fully open PTG position, a second weight M2 heavier than the first weight M1 is placed on the PTG to cause it to close under the load of the second weight M2. When the PTG approaches the fully closed position, the second weight M2 slides off the PTG and the first weight M1 pulls the PTG open again. The process is repeated to generate a consistent manual operation speed for thermal characterization. 
     The contribution of vibration to the manual operation of the motor  111  may also be verified, at step  2655 .  FIG. 31  illustrates an embodiment of measuring the contribution of vibration at a fully open position and a partially open position of the PTG. The PTG may be secured in the partially open position with a bungee cord or rope. If the obtained settings are confirmed, at step  2660 , to prevent overheat of the motor  111  in the manual operation conditions, at step  2665  the obtained settings are applied to the controller  115 , such as by saving the obtained settings in a parameter table or other lookup table. 
     Given the benefit provided by this disclosure, one of ordinary skill in the art will appreciate the various modifications and alterations within the scope of the fundamental concepts. While there has been shown and described what is at present considered the preferred embodiments, it will be appreciated by those skilled in the art that various changes and modifications can be made without departing from the scope of the invention defined by the following claims (e.g., the relative proportions and dimension of the components can be altered, and, where applicable, various components can be integrally formed or single components can be separated into multiple pieces).