Abstract:
The rotary orientation of a motor is determined using a resolver signal derived from the rotary orientation. In particular, the resolver signal is fed exclusively to a single control system that is arranged both for triggering and for evaluating the resolver signal.

Description:
CLAIM FOR PRIORITY  
         [0001]    This application claims priority to European Application No. 02002308.1 which was filed in the English language on Jan. 30, 2002.  
         TECHNICAL FIELD OF THE INVENTION  
         [0002]    A method and device for determining a rotary orientation of a motor, and in particular, through feeding a resolver signal derived from the rotary orientation to a single control system that is used for triggering and for evaluating the resolver signal, and a motor vehicle provided with such device.  
         BACKGROUND OF THE INVENTION  
         [0003]    Patent Application DE 100 57 674.5 (corresponding to U.S. Ser. No. 10/004,297) assigned to the present assignee and herein incorporated by reference, relates to the determining of an actual steering angle through measuring the travel of a steering gear rack. The present invention envisages to be used in much more universal fields of application where often no such rack would be present, and furthermore, in particular to save appreciably on the costs of external electronic chips. Notably, earlier determinations of the orientation angle took place through using an external electronic facility, in the form of an integrated circuit chip.  
         SUMMARY OF THE INVENTION  
         [0004]    The present invention provides a method using a resolver facility for generating sensing signals from the rotary orientation, which resolver facility feeds a single control facility both for triggering purposes and also for evaluating the resolver signals for subsequent use.  
           [0005]    In one embodiment of the invention, there is a method for determining the rotary orientation of a motor through using a resolver signal derived from the rotary orientation. For many purposes, such determining should be accurate while furthermore necessitating an inexpensive set-up. A particular, but non-limiting field of application, is the motor vehicle industry, and in particular, applications with respect to the various motors such as used in the electrically assisted steering of the vehicle (“power steering”), the water cooling facility, climate control, anti-roll stabilization, choke control, and other secondary facilities such as the starter generator. In particular, the latter application would require a fine resolution because of its field-oriented control.  
           [0006]    In one aspect of the invention, feeding such resolver signal exclusively to a single control system, that is furthermore arranged both for triggering and for evaluating the resolver signal.  
           [0007]    In another embodiment according to the invention, the method is preferably characterized by mapping such control system on a micro-controller or digital signal processor.  
           [0008]    According to still another embodiment of the invention, such method may advantageously be applied in a motor vehicle, and in particular to any one or more of an electrically assisted steering angle facility of such vehicle (“power steering”), a roll control facility, a fluid cooling facility, a climate control facility, a motor choke facility ( 150 ) and/or a vehicle starter generator facility.  
           [0009]    In another embodiment of the invention, there is a device for determining a rotary orientation of a motor, the device having a resolver facility with a resolver signal output for outputting a signal derived from the rotary orientation. According to the invention, such device is characterized by a feeding connection for feeding such resolver signal exclusively to a single control system the control system having a trigger output for triggering and an evaluating input for receiving an evaluation signal for evaluating the resolver signal.  
           [0010]    In another embodiment of such a device according to the invention, the system comprises a microcontroller or digital signal processor (hereinafter microcontroller) receiving at least two output signals from the resolver facility in parallel and having a single output for presenting the trigger signal to the resolver.  
           [0011]    Alternatively, the device is characterized by the microcontroller having an Analog-to-Digital converter fed by the two output signals.  
           [0012]    According to still another embodiment of the invention, such a device is preferably characterized in that the evaluating facility for the resolver signals has a tracking facility.  
           [0013]    An embodiment of the device according to the invention is characterized in that the microcontroller has a clock generating unit feeding a timer unit that generates the microcontroller output signal, the clock generating unit and timer unit furthermore together feeding the Analog to Digital Converter.  
           [0014]    Another embodiment of the device according to the invention is characterized in that the microcontroller has a clock generating unit feeding a Pulse Width Modulation Unit that generates the microcontroller output signal, the clock generating unit and Pulse Width Modulation unit furthermore together feeding the Analog to Digital Converter.  
           [0015]    Yet another embodiment of the device according to the invention is characterized in that the microcontroller has a clock generating unit feeding a Digital to Analog Converter, that generates the microcontroller output signal, the clock generating unit furthermore feeding the Analog to Digital Converter.  
           [0016]    In the above embodiments of the invention the clock generating unit uses a phase locked loop (PLL).  
           [0017]    The invention, in a preferred embodiment, is characterized by an evaluating unit for evaluating the resolver output signals through executing a tracking procedure.  
           [0018]    The tracking procedure is preferably based on: F(s)=Φ(s)/φ(s)=K 1 *(1+K 2 *s)/(s 2 +K 1  *K 2 *s+K 1 ), wherein Φ is the estimated rotor angle, φ is the actual rotor angle, K1 and K2 are filter parameters and s is the complex frequency.  
           [0019]    An embodiment of the device according to the invention is characterized by the microcontroller being furthermore provided with a phase shift compensating facility for effecting compensating for a phase shift of the resolver output signals.  
           [0020]    According to still another embodiment, the above Analog to Digital converter is arranged for operating as a parallel scan facility with respect to the resolver output signals.  
           [0021]    The Analog to Digital converter is preferably arranged to execute differential processing with respect to the resolver output signals as a correction measure for having interference signals on the respective signal interconnections canceling out.  
           [0022]    The invention furthermore relates to a motor vehicle provided with such device. 
       
    
    
     BRIEF DESCRIPTION OF THE INVENTION  
       [0023]    These and further aspects and advantages of the invention will be discussed more in detail hereinafter with reference to the disclosure of preferred embodiments, and in particular with reference to the appended Figures that show:  
         [0024]    [0024]FIG. 1 is a diagram of a resolver facility.  
         [0025]    [0025]FIG. 2 shows evaluation of the resolver output signals according to a first principle.  
         [0026]    [0026]FIG. 3 shows signal generation in a microcontroller that is provided with a timer unit.  
         [0027]    [0027]FIG. 4 shows output signals from the timer module and from the resolver.  
         [0028]    [0028]FIG. 5 shows signal generation in a microcontroller that has a pulse width modulation unit.  
         [0029]    [0029]FIG. 6 shows output signals from the pulse width modulation unit and from the resolver.  
         [0030]    [0030]FIG. 7 shows signal generation in a microcontroller that has a digital to analog converter.  
         [0031]    [0031]FIG. 8 shows output signals from the digital to analog converter and from the resolver.  
         [0032]    [0032]FIG. 9 shows an angle monitoring.  
         [0033]    [0033]FIG. 10 shows a motor vehicle provided with various subsystems embodying the invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0034]    [0034]FIG. 1 illustrates a functionality diagram of a resolver facility. Such resolvers have been in use where the rotor orientation of an electric driving motor must be monitored with high resolution and accuracy. By itself, such resolver can be considered as a self-rotating transformer. The required input signal is a sinusoid, and the two parallel output signals are amplitude modulated signals that for an orthogonal construction are designated as sinusoid and cosinusoid, respectively. In principle, other orientations could be feasible, as well as the use of more than two output sensing coils. The input signal for the resolver, as well as the output signals therefrom, are processed in electric driving systems through analog or digital evaluating devices, such as building block AS2S1000, manufactured by Analog Devices, Inc. According to the present invention, the input signals to the resolver, as well as the output signals from the resolver, are exclusively processed through a Digital Signal Processor DSP, or microcontroller. In particular, the evaluation uses the so-called tracking methodology.  
         [0035]    In FIG. 1, the resolver shown can be used for monitoring both the angular position φ as well as the angular velocity dφ/dt. As shown, the main sensing elements are the sensing coils  28 ,  30  that are positioned circularly in radial orientation around the rotating part  26 . The central rotating part  26  is fixed to the rotating axis and constitutes a coupling element between excitation on terminals  20  and the sensing coils  28 ,  30 . At right in the Figure, the excitation signal at the top will induce the modulated signals in the sine and cosine coil, that have amplitudes with sinusoidal and cosinusoidal variation, respectively. The envelope of the two signals has a substantially 100% modulation depth. The rotating part may be executed in the form of the primary coil as shown. Another implementation has a stationary inductive coil, whereas the rotary part would then constitute an inductive coupler with an angularly variable coupling factor.  
         [0036]    [0036]FIG. 2 illustrates the evaluating of the resolver output signal according to the tracking (German: Nachlauf) principle. The resolver facility  36  with excitation facility  38  and the instantaneous angular position φ have been clearly shown. As shown, the resolver outputs are Asin(φ) and Acos(φ) that feed multipliers  40  and  42 . The outputs Asin(φ) and Acos(φ) are obtained from the modulated resolver signals Asin(ωt)*sin(φ) and Asin(ωt)*sin(φ) by sampling this signals exactly at the maximum or minimum of the carrier signal Asin(ωt) where ω is the circular frequency of this signal and t is the time. Subtracting the two products Asin(φ) and Acos(φ) in subtractor  44  followed by standard calculation steps yields the input to angle monitor  46 , that furthermore by means of function generators  48 ,  50  outputs two quantities sin(Φ) and cos(Φ), respectively, for feeding the two multipliers  40  and  42 . The sinusoidal excitation voltage is presented:  
         [0037]    U exc =Û*sin(ωt+δ res ), wherein the successive quantities are the excitation voltage, the excitation amplitude, the circular frequency of the excitation signal, the time, and a phase shift angle. The latter is a property of the geometrical realization.  
         [0038]    In the calculation, Φ is an estimated rotational angle, so that (φ−Φ) is the deviation, that must be controlled towards a zero value. Herein, sin(φ−Φ) is approximated by (φ−Φ) for small values of the difference (φ−Φ).  
         [0039]    [0039]FIG. 3 illustrates a signal generation embodiment through using a microcontroller  52  that is provided with a timer unit  72  and an Analog to Digital converter  68 . Resolver  36  has two output connection pairs  60 / 62  and  64 / 66  for the two output signals that feed an Analog to Digital Converter  68 . An internal counter not separately shown in the timer module  72 , fed by a clock generating unit  70 , which use a Phase Locked Loop, is used as frequency divider and generates from the internal microcontroller bus clock a two-valued block signal with a duty cycle of 50% and a frequency that is appropriate for the excitation. In a low-pass filter  56 , which is connected to the output pin  54  of the timer unit  72 , the basis frequency wave is filtered out from the two-valued signal and applied at low output impedance through buffer or amplifier  58  to the excitation coil of resolver  36 . The filtering will cause a certain phase delay. This will likewise cause a phase shift in the secondary output signals to microcontroller  52 .  
         [0040]    The microcontroller  52  can be a conventional building block featuring a processor, program ROM, data RAM, memory management, interconnection among these items, and an external communication facility. Various other features could be present in addition, and persons skilled in the art would know how to choose among such commercially available products in view of temporal and spatial resolution of the angles that would be necessary, and possibly, in view of other tasks that the device in question should execute. Also, the programming of the microcontroller would by itself straightforward. Alternatively, an also commercially available building block Digital Signal Processor could be used in lieu of the microcontroller. For brevity and convenience, hereinafter the description refers to a microcontroller, which referring should include also a Digital Signal Processor.  
         [0041]    [0041]FIG. 4 illustrates output signals from the timer module and the resolver shown in FIG. 3. To compensate for the phase delay, a further counter of the timer module, not shown for brevity, is driven as a monostable flipflop with a delayed trigger, of which the delay can be adjusted. The rising signal edge is used for controlling the Analog to Digital Converter. This emphasizes the necessity for using a microcontroller that has an Analog to Digital Converter which can be triggered by the timer module  72 . The pulse length of the Monoflop output is irrelevant but should lie in an interval corresponding to the requirements posed by the microcontroller. The sensing of the resolver signals at the maximum value is necessary for demodulating the signal in question. Therefore, the Analog to Digital Converter produces immediately the demodulated signals sin(φ) and cos(φ), respectively. The successive curves in FIG. 4 represent the signal at the output pin of the timer module ( 71 ), the signal at the input of the resolver ( 73 ), the signal at the sine output of the resolver ( 75 ), the signal at the cosine output of the resolver ( 77 ), and the signal at the sync-input of the AD converter ( 79 ).  
         [0042]    [0042]FIG. 5 illustrates signal generation in a microcontroller  74  that has PLL unit  70  and a Pulse Width Modulation unit  76 , corresponding elements carrying the same reference numerals as in FIG. 3. Through the PWM unit  76 , indirectly a sinusoidal voltage is modulated. The pulse width of the PWM signal changes along with the amplitude of the excitation signal to be generated. On the one hand, a somewhat greater amount of calculation is necessary in microcontroller  74 . On the other hand, the requirements to analog low-pass filter  56  are less than before. In this embodiment, the microcontroller  74  will advantageously offer trigger signals to the Analog to Digital converter through the PWM module  76 .  
         [0043]    [0043]FIG. 6 illustrates the output signals from the pulse width modulation and the resolver. The delay in converting the input signals with respect to the generating of the excitation frequency is also brought about by the PWM module. The conversion is started upon attaining a prespecified number of n pulses after arriving at the maximum. This demodulates the resolver signal. The successive curves in FIG. 6 represent the signal at the output pin of the PWM module ( 81 ), the signal at the input of the resolver ( 83 ), the signal at the sine output of the resolver ( 85 ), the signal at the cosine output of the resolver ( 87 ), and the signal at the sync-input of the AD converter ( 89 ).  
         [0044]    [0044]FIG. 7 illustrates the signal generation in a microcontroller  90  that has a Digital to Analog converter  92 , in addition to various elements corresponding to those of FIG. 5 and carrying the same reference numerals. The excitation voltage is outputted directly via the Digital to Analog Converter. This will furthermore decrease the requirements to the filtering of the signals in filter  56 . The microcontroller software must provide for starting the generation of the excitation voltage through the Digital to Analog Converter and the converting of the operation of the Analog to Digital Converter proper.  
         [0045]    [0045]FIG. 8 illustrates output signals from the digital analog converter  92  and the resolver  36 . The successive curves in this Figure represent the signal at the output pin of the Digital to Analog Converter ( 91 ), the signal at the input of the resolver ( 93 ), the signal at the sine output of the resolver ( 95 ), the signal at the cosine output of the resolver ( 97 ), and the signal at the sync-input of the AD converter ( 99 ). The respective delays eventually result in a value At as shown.  
         [0046]    Either under control of a SYNC signal, or through a software activation, the Analog to Digital Converter will repeatedly start a next Analog Conversion Scan. If the Analog Digital Conversion allows parallel scanning of four input signals, the resolver signals may be read in a differential manner. The simultaneous reading of two input signals should be guaranteed as being correct at higher resolver frequencies relative to the clock frequency of the microcontroller. Otherwise, the parallel operation could cause angle errors that were variable with angular velocity.  
         [0047]    Differential transfer of secondary resolver signals to the Analog to Digital Converter would to an appreciable degree compensate for interference signals on the signal interconnections, because these signals would be coupled to the twisted connections with an identical phase, and so largely cancel out.  
         [0048]    Through sensing the Sine and Cosine resolver output signals at their maximum points, the signal will be demodulated. This immediately yields the signals sin(φ) and cos(φ), according to the following expressions:  
         Û*sin(ω*t+δ res )*sin(φ)—demodulation→A*sin(φ)  
         Û*sin(ω*t+δ res )*cos(φ)—demodulation→A*cos(φ)  
         [0049]    Herein, Û is the amplitude of the excitation signal, ω is the circular frequency of the excitation signal, t is the time, δ res  is the angular phase shift and φis the actual rotor angle.  
         [0050]    [0050]FIG. 9 illustrates a functionality diagram of the angle monitoring. Inputs  100 ,  102  receive the two resolver signals. Various processing elements are multipliers  104 ,  108 , subtractor  106 , adder  118 , the proportional amplifier with amplification K 1    110  and K 2    116 , the integrators  112  and  114 , and the generating of the sine and cosine functions, respectively of the estimated angle Φ,  122 ,  124 . The principal functions are thereby those of an integrator and of a PI controller. This setup strives to adjust the discrepancy between actual rotor angle φand the estimated (by the angle monitoring control loop in FIG. 9) angle Φ to zero. The transfer function is as follows:  
         F(s)=Φ(s)/φ(s)=K 1 *(1+K 2 *s)/(s 2 +K 1 *K 2 *s+K 1 ),  
         [0051]    wherein the various parameters have been indicated supra. The parameters can be set according to the particular system constants. Advantageously, the monitoring will be executed completely in software on the microcontroller.  
         [0052]    [0052]FIG. 10 illustrates a motor vehicle provided with various subsystems each embodying the invention. The vehicle has succinctly been indicated by the vehicle body  130 , front ( 132 ) and rear wheels ( 134 ), main engine  148 , and steering wheel  136 . Most of the remaining constructions and facilities have been omitted for brevity; inasmuch as by themselves, persons skilled in motor vehicle art and various subfields thereof would know how to design such conventional facilities.  
         [0053]    Steering wheel column  138  has been provided with an electric motor  140  for implementing so-called “power steering”, to thereby diminishing the necessary exertions by a driving person. The rotary angle and/or angular velocity of the steering column are evaluated in a control device  142  according to the invention, for as based thereon generating control signals to drive motor  140 .  
         [0054]    Main engine  148  during operation is being cooled by a coolant loop  149 . For optimum fuel efficiency, the coolant stream is controlled by a valve  156 , that itself is driven by a rotary motor  154 . In similar manner as regards motor  140 , the position of motor  154  is evaluated by a device according to the present invention for so effecting further control such as feed-back operations, not shown for clarity.  
         [0055]    For reasons of anti-roll stabilization, rear wheel(s)  134  have been provided with a suspension facility  158  and including parts thereof that may have their operating parameters such as stiffness or bias position controlled by a rotary motor, or by another device that ultimately effects a rotary motion. Through element  160 , such rotary position and/or temporal differentials thereof are sensed by device  160  according to the present invention, whereupon the measured parameter values can be used for controlling the above operational parameters.  
         [0056]    Further subsystems that may have a device installed according the present invention, but which have for reasons of brevity been shown in no more than blockwise representations are the following. Climate control  144  uses a valve  146  for regulating various air currents and/or air temperatures. The rotary motor that drives valve  146  may have been provided with the facilities according to the present invention. Choke control facility  150  in its turn may have a valve or other parts that have their positions controlled by a rotary motor and including a facility embodying the present invention. Starter generator  152  in its turn may have a valve or other parts that have their positions controlled by a rotary motor and including a facility embodying the present invention.  
         [0057]    In the above, the present invention has been disclosed by reference to various preferred embodiments. Nevertheless, persons skilled in the art would from reading the disclosure recognized various changes and modifications. Therefore, the description should be taken by way of instruction rather than by way of limitation.