Torque limiting system and method for DC motor

Abstract

Technical solutions for controlling a brushed direct current (DC) motor are described, including: determining a brush voltage drop across a set of brushes of the brushed DC motor based on one of a motor current command or an actual motor current; determining, based on the brush voltage drop, at least one of: a first torque limit that does not exceed a supply current limit based on a supply current value, and a second torque limit that does not exceed a maximum available voltage based on a controller supply voltage value; determining a final torque limit based on at least one of the first torque limit and the second torque limit; determining a limited torque command based on the torque command and not exceeding a final torque limit; determining a voltage command based on the limited torque command; and applying a DC voltage to the brushed DC motor based on the voltage command.

Description

Technical Field

[0001] The present disclosure relates to methods and systems for operating a DC motor, such as a brushed DC motor. More specifically, the present disclosure relates to methods and systems for limiting the torque of a DC motor. Background Art

[0002] Brushed DC motors are used in a variety of applications. One such application of brushed DC motors is in power steering systems for vehicles. Significant advantages of brushed DC motors include low cost components, less circuitry, simplicity, and ease of control when compared to alternatives such as AC motors.

[0003] Active speed control techniques can be used with brushed DC motors to reduce noise and provide better customer performance. There are two main methods for controlling speed: one method utilizes a speed-torque controller and the other utilizes a speed-voltage controller.

[0004] Several different operating constraints may apply to the operation of a DC motor, such as available voltage, supply current limits, and motor current limits. Summary of the invention

[0005] According to one or more embodiments, a method for controlling a brushed direct current (DC) motor includes: determining a brush voltage drop across a set of brushes of the brushed DC motor based on one of a motor current command or an actual motor current; determining at least one of the following based on the brush voltage drop: a first torque limit based on a supply current value not exceeding a supply current limit, and a second torque limit based on a controller supply voltage value not exceeding a maximum available voltage; determining a final torque limit based on at least one of the first torque limit and the second torque limit; determining a limited torque command based on the torque command and not exceeding the final torque limit; determining a voltage command based on the limited torque command; and applying a DC voltage to the brushed DC motor based on the voltage command.

[0006] According to one or more embodiments, a motor control system is provided. The motor system includes: a brushed DC motor having a set of brushes; a voltage regulator configured to apply a DC voltage to the brushed DC motor based on a voltage command; and a controller configured to: determine a brush voltage drop across a set of brushes of the brushed DC motor based on one of a motor current command or an actual motor current; determine at least one of the following based on the brush voltage drop: a first torque limit based on a supply current value not exceeding a supply current limit, and a second torque limit based on a controller supply voltage value not exceeding a maximum available voltage; determine a final torque limit based on at least one of the first torque limit and the second torque limit; determine a limited torque command based on the torque command and not exceeding the final torque limit; determine a voltage command based on the limited torque command; and transmit the voltage command to the voltage regulator.

[0007] These and other advantages and features will become more apparent from the following description taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] The subject matter of the present disclosure for which protection is sought is particularly pointed out and defined in the claims at the end of this specification. The foregoing and other features and advantages of the present disclosure are apparent from the following detailed description in conjunction with the accompanying drawings, in which:

[0009] Figure 1 A column position module (CPM) of a steering system in a vehicle according to various aspects of the present disclosure is shown;

[0010] Figure 2 A schematic block diagram of a system for controlling a brushed DC motor according to various aspects of the present disclosure is shown;

[0011] Figure 3 An electrical schematic diagram of a control system for a brushed DC motor according to various aspects of the present disclosure is shown;

[0012] Figure 4 A schematic block diagram of a motor controller for operating a DC motor according to various aspects of the present disclosure is shown;

[0013] Figure 5 A schematic diagram showing a torque command generator of a motor controller according to various aspects of the present disclosure is shown;

[0014] FIG. 6A to FIG. 6C Graphs showing speed, torque, and motor current, respectively, of a DC motor operated in accordance with satisfying a motor current limit on a common time scale are shown in accordance with various aspects of the present disclosure;

[0015] 7A to 7CGraphs showing speed, torque and motor current, respectively, of a DC motor operated in accordance with satisfying supply current limits on a common time scale are shown in accordance with various aspects of the present disclosure;

[0016] FIG. 8A to FIG. 8C Graphs showing speed, torque and motor current, respectively, of a DC motor operated in accordance with satisfying supply voltage constraints on a common time scale are shown in accordance with various aspects of the present disclosure;

[0017] Fig. 9 shows a graph showing torque produced by a DC motor over a period of time using the disclosed method and two alternative techniques for operating a DC motor, each of which includes estimating brush voltage drop; and

[0018] Fig.10 A flow chart listing steps in a method for operating a DC motor according to various aspects of the present disclosure is shown. DETAILED DESCRIPTION

[0019] Reference is now made to the accompanying drawings, wherein the present disclosure will be described with reference to specific embodiments, rather than limiting the present disclosure, it being understood that the disclosed embodiments are merely illustrative of the present disclosure, which may be embodied in various forms and alternative forms. The drawings are not necessarily drawn to scale, and some features may be enlarged or reduced to show details of particular components. Therefore, the specific structural and functional details disclosed herein should not be construed as limiting, but merely as a representative basis for teaching those skilled in the art to adopt the present disclosure in various ways.

[0020] As used herein, the terms module and submodule refer to one or more processing circuits, such as application specific integrated circuits (ASICs), electronic circuits, processors (shared, dedicated, or groups) and memories that execute one or more software or firmware programs, combinational logic circuits, and / or other suitable components that provide the described functionality. As can be appreciated, the submodules described below can be combined and / or further divided.

[0021] The present disclosure provides an anti-saturation control strategy for a speed-torque controller for operating a brushed DC motor. The motor torque can be limited to meet several different operating constraints. The present disclosure deals with three such operating constraints, including maximum available voltage, supply current limit, and motor current limit. Equations are derived that relate these operating constraints to maximum and minimum torques. The derivation changes with system state and provides active limits and maximum capabilities.

[0022] In some embodiments, a torque limit corresponding to a maximum available voltage and supply current limit can be determined based on a brush voltage drop across a set of brushes of a brushed DC motor. The present disclosure is provided for determining a brush voltage drop based on a motor current command or an actual motor current, and determining a torque limit value corresponding to a brushed DC motor that satisfies each of a supply current limit and a motor current limit based on the brush voltage drop. The systems and methods of the present disclosure are shown to provide enhanced output torque while satisfying operating constraints, and the computational burden is significantly reduced compared to alternative techniques using iterative solvers, compared to alternative techniques using iterative solvers.

[0023] Referring now to the accompanying drawings, in which the technical solution will be described with reference to specific embodiments but not limited thereto, Figure 1 An exemplary embodiment of a column position module (CPM) 20 of a steering system in a vehicle is shown, which may utilize the disclosed systems and methods to control a DC motor.

[0024] The CPM 20 includes a steering shaft 22 configured to be attached to a steering wheel, which may also be referred to as a hand wheel, which a person may use to steer the vehicle. The CPM 20 includes a steering actuator 24 attached to the steering shaft. The steering actuator 24 may supplement the force applied by the person to provide a power-assisted steering function. The CPM 20 also includes a telescopic actuator motor 26 configured to control the axial position of the hand wheel by moving the steering shaft 22 in an axial direction. The CPM 20 also includes a roll actuator motor 28 configured to control the vertical position of the hand wheel by moving the end of the steering shaft in a radial direction.

[0025] Any or all of the steering actuator 24, telescopic actuator motor 26, and / or roll actuator motor 28 may include brushed DC motors and may be controlled using the systems and methods of the present disclosure. However, the systems and methods of the present disclosure may be used with brushed DC motors in other vehicle applications, such as for window or lock actuators. The systems and methods of the present disclosure are not limited to use in vehicles and may be used with brushed DC motors in a variety of different applications.

[0026] Figure 2 2 shows a schematic block diagram of a system 50 for controlling DC motors 26, 28. In some embodiments, as Figure 2As shown in FIG. 1 , the DC motor 26, 28 is a brushed DC motor having a set of brushes 30, 32 for transmitting DC current from a fixed terminal to a rotor winding of the DC motor 26, 28. The set of brushes 30, 32 includes a first brush 30 configured to be connected to a power source for receiving DC current. The set of brushes 30, 32 also includes a second brush 32 configured to be connected to a current absorbing load (such as a ground terminal).

[0027] The system 50 includes a controller 60. The controller 60 may include any suitable controller, such as an electronic control unit or other suitable controller. The controller 60 may be configured to control various functions of, for example, a steering system and / or various functions of a vehicle. The controller 60 may include a processor 62 and a memory 64. The processor 62 may include any suitable processor, such as those described herein. Additionally or alternatively, the controller 60 may include any suitable number of processors other than or different from the processor 62. The memory 64 may include a single disk or multiple disks (e.g., a hard disk drive), and include a storage management module that manages one or more partitions within the memory 64. In some embodiments, the memory 64 may include a flash memory, a semiconductor (solid-state) memory, and the like. The memory 64 may include a random access memory (RAM), a read-only memory (ROM), or a combination thereof. The memory 64 may include instructions that, when executed by the processor 62, cause the processor 62 to at least control various aspects of the vehicle. Additionally or alternatively, the memory 64 may include instructions that, when executed by the processor 62, cause the processor 62 to perform functions associated with the systems and methods described herein.

[0028] The controller 60 may be operably connected to the voltage regulator 52. The voltage regulator 52 may be configured to apply a DC voltage v to the first brush 30 of the DC motor 26, 28. The voltage regulator 52 may be based on a voltage command v from the controller 60. cmd To generate a DC voltage v.

[0029] In some embodiments, Figure 2 As shown, the system 50 may include a current sensor 54 configured to measure the DC current applied to the DC motors 26, 28 and to generate a motor current signal i m The motor current signal is transmitted to the controller 60 and represents the actual motor current in the windings of the DC motors 26, 28. Additionally or alternatively, Figure 2 As shown in FIG. 1 , the system 50 may include a position sensor 56 configured to measure the rotational position of the DC motors 26, 28 and convert the motor position signal ω into a rotational position signal ω. m Transmitted to the controller 60.

[0030] In some embodiments, the controller 60 can perform the methods described herein. However, the execution of the methods described herein by the controller 60 does not mean limitation, and any type of software executed on a controller or processor can perform the methods described herein without departing from the scope of the present disclosure. For example, a controller (such as a processor executing software within a computing device) can perform the methods described herein.

[0031] Figure 3 1 shows an electrical schematic diagram of a control system for brushed DC motors 26, 28. As shown, the controller 60 and the DC motors 26, 28 define a supply current i S The voltage loop defines the battery voltage V across the power source (not shown). BATT and the controller supply voltage V across the controller 60 ECU .like Figure 3 As shown, the voltage loop includes the battery harness resistance R in the current path between the battery and the controller 60 BH The voltage loop also includes a controller input resistor R in the controller 60. C , which is related to the battery harness resistance R BH The DC motors 26 and 28 are connected in series. Figure 3 It is shown as including an inductor, a resistor and a voltage source connected in series, representing the winding inductance, the coil resistance and the back electromotive force, respectively.

[0032] Figure 4 A schematic block diagram of a motor controller 70 for operating a DC motor according to various aspects of the present disclosure is shown. The motor controller 70 is configured as a speed-torque controller. However, the principles of the present disclosure may be applied to other controller configurations.

[0033] The motor controller 70 includes a subtractor 72 configured to obtain a speed command signal ω from the speed command signal ω. ref Subtract the motor speed ω m , and calculate the speed command signal ω ref and motor speed ω m The speed difference signal ω diff The motor controller 70 further includes a torque command generator 74 configured to generate a torque command based on the speed difference signal ω diff To generate the torque command signal τ cmd The torque command generator 74 may use a proportional-integral (PI) control loop to generate a torque command signal τ cmd , however, other control techniques may be used, such as a proportional-integral-derivative (PID) control loop or a lookup table.

[0034] The motor controller 70 further includes a torque limiter 76 configured to set a torque based on the torque command signal τ cmd To generate the limited torque command τ cmdlim The torque limiter 76 also takes as input three operating constraints for operating the DC motors 26, 28, including:

[0035] Motor current limit I MAX ;

[0036] Supply current limit value I slim ;as well as

[0037] Maximum available voltage V MAX .

[0038] The torque limiter 76 also generates an anti-saturation signal AW, which indicates the limited torque command τ cmdlim is limited so that the DC motors 26, 28 satisfy the operating constraints I MAX ,I slim 、V MAX The anti-saturation signal AW is applied from the torque limiter 76 to the torque command generator 74.

[0039] The motor controller 70 also includes a torque regulator 78 configured to adjust the torque based on the limited torque command τ cmdlim To generate the current command i cmd In some embodiments, the torque regulator 78 controls the torque control by setting the limited torque command τ cmdlim Divide by the back electromotive force constant K to generate the current command i cmd .

[0040] The motor controller 70 further includes a current regulator 80 configured to adjust the current based on the current command i cmd To generate the voltage command v cmd In some embodiments, Figure 4 As shown, the current regulator 80 converts the motor current signal i m The current regulator 80 can use a control loop (such as a PI control loop) based on the current command i cmd and the motor current signal i m The voltage command v is calculated by the difference between cmd Alternatively or additionally, the current regulator 80 may use a reference model (such as an equation or a lookup table) to calculate the current command i based on the current command i cmd and the motor current signal i m To determine the voltage command v cmd .

[0041] The following equations (1)-(2) show the mathematical model of the DC motor.

[0042]

[0043] Here, v is the voltage applied to the DC motor, i is the motor current, R is the resistance, L is the inductance, K is the back EMF constant, J is the inertia of the motor, ω is the motor speed, and τ e is the generated electrical torque, τ LF is the load plus friction torque.

[0044] The following equation (3) describes the brush voltage drop v due to brushes 30, 32: b . V 0 is the brush voltage parameter of the motor, I 0 is the motor current parameter.

[0045] Brush voltage drop v b occurs in the direction of the motor current i, as described by equation (3).

[0046]

[0047] The generated electrical torque τ e is directly related to the motor current as described in equation (4).

[0048] τ e =Ki (4)

[0049] The following equation (5) provides a general method for calculating the torque command from the actual speed and the reference speed using a PI control loop. The load-friction torque curve based on the motor position can be added as a feedforward term in equation (5).

[0050] τ cmd =K p (ω ref -ω m )+K i ∫(ω ref -ω)dt (5)

[0051] Among them, K p Indicates the proportional gain value, K i Indicates the integral gain value. Proportional gain value K p and / or integral gain value K i Either or both of can be constants.

[0052] The present disclosure provides three different operating constraints for the DC motors 26, 28 and can be used for the anti-windup function of the PI control loop described in equation (5). These operating constraints include:

[0053] Motor current limit value I MAX ;

[0054] Supply current limit I slim ;as well as

[0055] Maximum available voltage V MAX .

[0056] The torque command can be limited to satisfy each of these operating constraints. The following section provides a derivation of the maximum torque and minimum torque based on these constraints. Table I below lists the motor parameters used to verify the method and system of the present disclosure. Voltage mode operation can be used with the speed-torque controller pole set to -20.

[0057] parameter symbol value resistance R 0.833602905Ω inductance L 0.8mH BEMF constant K 0.030281067Vs / rad Brush voltage parameters <![CDATA[V 0 ]]> 4.1472V Brush current parameters <![CDATA[I 0 ]]> 12A Inertia J <![CDATA[1.0581×10 -5 kg / m 2 ]]> Viscosity constant B 0.000545Nms / rad

[0058] Table I: Parameter values

[0059] Figure 5 Schematic diagram of the torque command generator 74 of the motor controller 70 is shown. The torque command generator 74 may implement a PI control loop as described in equation (5). The torque command generator 74 includes a first gain block 82 configured to convert the speed difference signal ω diff and proportional gain value K p The torque command generator 74 further includes an adder 84 configured to calculate a torque command signal τ based on the output of the first gain block 82. cmd .

[0060] The torque command generator 74 further includes an integrator 86 configured to calculate the speed difference signal ω diff The torque command generator 74 also includes a second gain block 88, which is configured to convert the speed difference signal ω diff The integral and integral gain value K i The output of the second gain block 88 is provided to the adder 84, which calculates the torque command signal τ based on the sum of the output of the first gain block 82 and the output of the second gain block 88. cmd .

[0061] In some embodiments, Figure 5 As shown, the anti-windup signal AW is provided to the integrator 86. The integrator 86 may suspend operation in response to receiving the anti-windup signal AW, thereby indicating that the limited torque command is set based on the torque limit to meet the operating constraint I MAX ,I slim 、V MAX At least one of .

[0062] Motor current limit I MAX

[0063] Maximum torque τ based on motor current MAX_im and the minimum torque τ based on the motor current MIN_im , each based on not exceeding the maximum motor current value I MAX The motor current i can be limited according to the motor current I MAX To calculate, as described in equation (6) and equation (7):

[0064] τ MAX_im = KI MAX (6)

[0065] τ MIN_im = –KI MAX (7)

[0066] FIG. 6A to FIG. 6C The diagram shows the motor current limit I on a common time scale. MAX Graphs of speed, torque, and motor current for DC motors 26, 28 operating at 5.0 amps (A). Fig. 6A The speed command signal ω is shown ref (also referred to as reference speed), and a first curve 102 showing the motor speed ω m A second curve 104 of the actual motor speed (also referred to as actual motor speed) is shown.

[0067] Limited torque command τ cmdlim Based on the maximum torque τ based on the motor current from equations (6) and (7) respectively MAX_im and the minimum torque τ based on the motor current MIN_im The motor current limit I is set to 5.0A in the region of the reference speed between 2650 rpm and -2650 rpm. MAX . Limit the torque command τ cmdlim These regions where the system 50 satisfies one or more operating constraints may be referred to as anti-saturation regions.

[0068] Figure 6B Including limited torque command τ cmdlim The third curve 106, wherein the first line 108 shows the positive motor current limit I MAX The maximum torque τ based on the motor current corresponding to the DC motors 26 and 28 operating in the positive speed direction at the same time is +5.0A MAX_im . Figure 6B A second line 110 is also included, which shows the relationship between the negative motor current limit -I MAX The minimum torque τ based on the motor current corresponding to the DC motors 26 and 28 is -5.0A and operates in the negative speed direction at the same time MIN_imThe limiting method can be verified if the actual motor current i reaches ±5 A at the beginning of anti-saturation and stays at this limit throughout the anti-saturation region.

[0069] Figure 6C A fourth curve 112 including a motor current i, a first line 114 and a second line 116, wherein the first line 114 shows the motor current limit I of positive polarity (ie, forward operation). MAX , the second line 116 shows the negative motor current limit -I for negative polarity (ie, reverse operation) MAX . Figure 6C The exact behavior of the motor current i is shown and the appropriate maximum motor current I is verified MAX , -I MAX restrictions.

[0070] Supply current limit I slim

[0071] The ECU voltage V ECU At, the supply current limit I slim This ultimately limits the power that can be delivered or absorbed by the battery. The motor power formula can be written as described in equation (8):

[0072]

[0073] Under the constraints, the relationship can be described by equation (9):

[0074]

[0075] Here, R c is the controller resistance, I MS The supply current is limited to I slim The maximum motor current.

[0076] Alternative controllers can ignore or simplify the brush voltage drop v b To solve I MS One such alternative design assumes a brush voltage drop of v b Equal to the brush voltage parameter V 0 and have a constant value, thus neglecting the exponential term. This simplification may lead to several problems. For small motors, these two terms can be much larger than expected. On the other hand, if the value of the supply current is reduced due to some unfavorable condition, then the brush current I 0 Compared with the maximum motor current I MS cannot be considered high. Therefore, under such conditions, consider the brush voltage drop v b May result in lower I MSThis can be particularly problematic under adverse conditions when it is desired to obtain the maximum possible torque while satisfying operating constraints. To correctly solve this equation, the most conventional approach is an iterative method. However, iterative methods can require significant computational burden and cost.

[0077] The actual motor current i can be used to calculate the brush voltage drop v b , and the brush voltage drop v b Can be used to solve the supply current limit I MS The first step is therefore to use equation (3) to find the brush voltage drop v for the specific conditions. b Considering the brush voltage drop v b , equation (9) can be rewritten as equation (10):

[0078]

[0079] The two solutions of equation (10) can be specified as the maximum motor current and the minimum motor current for the supply current limit, as described in equations (11)-(12) below:

[0080]

[0081] This approach may have some disadvantages. If the brush voltage drop v b is not significant during limiting conditions, the proposed method provides a solution that is very close to the actual solution of equation (9) under all conditions. The solution of the proposed method is only b Very significant and the actual current is far from I MS However, even with a significant brush voltage drop v b When the motor current approaches the maximum value I MS , the proposed solutions are also very close to the actual solutions and ensure proper restrictions when needed.

[0082] Maximum torque τ based on supply current MAX_is and the minimum torque τ based on the supply current MIN_is , each based on not exceeding the supply current limit I slim The supply current value I s , can be limited according to the supply current I slim To calculate, as described in equation (13) and equation (14):

[0083]

[0084] 7A to 7C shows the operation to meet the supply current limit I slimGraphs of speed, torque, and motor current for a 2.0 ampere (A) DC motor 26, 28. Fig. 7A The speed command signal ω is shown ref (also referred to as reference speed) and a fifth curve 122 showing the motor speed ω m (also referred to as actual motor speed) .

[0085] Limited torque command τ cmdlim Based on the maximum torque τ based on the supply current from equations (13) and (14) respectively MAX_is and the minimum torque τ based on the supply current MIN_is The controller 60 is limited to meet the supply current limit I of 2.0A in the area above 1641rpm and below -1641rpm. slim .

[0086] Figure 7B Including limited torque command τ cmdlim The seventh curve 126, wherein the first line 128 shows the motor current limit I MAX , while the controller 60 operating in the positive speed direction corresponds to the maximum torque τ based on the supply current MAX_is . Figure 7B A second line 130 is also included, which shows the current limit I MAX , the minimum torque τ corresponding to the DC motors 26 and 28 operating simultaneously in the negative speed direction MIN_is .

[0087] Figure 7C Including the supply current i s The eighth curve 132, the first line 134 and the second line 136 of FIG. 13 are shown, wherein the first line 134 shows the supply current limit I of 2.0A for positive polarity (ie, forward operation). slim , the second line 136 shows a negative supply current limit of -2.0A for negative polarity (ie, reverse operation). slim . Figure 7C shows the supply current i s The exact operation and verification of proper supply current limiting I slim , -I slim restrictions.

[0088] Maximum available voltage V MAX

[0089] The maximum available voltage can be described as in equation (15):

[0090]

[0091] Under the constraints, equation (15) can be expressed as equation (16):

[0092]

[0093] Here, I MV The maximum available voltage V is taken into account MAX The current limit. In the case where the current does not change significantly at the limit condition, the dynamic term can be considered negligible. Note here that we use different variables for the maximum available voltage, because the full battery or controller supply voltage V ECU may not be applicable when applying the controller 60 to the DC motors 26, 28. Without using an iterative method, the equation becomes very difficult to solve. As mentioned above, the iterative solution requires considerable computational cost. In addition, for more robust operation and simplicity, zero values ​​are not used as the maximum or minimum limits at any point.

[0094] The system and method of the present disclosure can calculate the brush voltage drop v based on the actual motor current i b , thereby eliminating the exponential term Therefore, the method disclosed in the present invention can first use equation (3) to calculate the brush voltage drop v in real time. b , then consider the maximum available voltage I MV Solving for Current Limit. Equation (17) and equation (18) show the solutions for positive current limit and negative current limit.

[0095]

[0096] Maximum torque τ based on supply voltage MAX_vs and the minimum torque τ based on the supply voltage MIN_vs , each based on not exceeding the maximum available voltage V MAX The required controller supply voltage V ECU , according to the maximum available voltage V MAX To calculate, as described in equation (19) and equation (20):

[0097]

[0098] This method provides a MV The solution can deviate slightly when the motor current i is far from the limit, where torque limitation based on the available voltage is not necessary.

[0099] FIG. 8A to FIG. 8C The diagram shows the operation to meet the maximum available voltage (also called supply voltage limit) V on a common time scale. MAXGraphs of speed, torque and motor current for 13.5V DC motors 26, 28. Fig. 8A The speed command signal ω is shown ref The ninth curve 142 of the motor speed ω is also referred to as the reference speed, and m A tenth curve 144 of the actual motor speed (also referred to as actual motor speed).

[0100] Limited torque command τ cmdlim Based on the maximum torque τ based on the supply voltage from equations (19) and (20) respectively MAX_vs and the minimum torque τ based on the supply voltage MIN_vs Limitation is performed so that the controller 60 meets the supply voltage limit of 13.5V in the area above 2557rpm and below -2557rpm.

[0101] Figure 8B Including limited torque command τ cmdlim 146, wherein the first line 148 shows the maximum torque τ based on the supply voltage corresponding to the controller 60 satisfying the supply voltage limit of 13.5V while operating in the positive speed direction MAX_vs . Figure 8B Also included is a second line 150 showing the minimum torque τ corresponding to the controller 60 satisfying the supply voltage limit of 13.5V while operating in the negative speed direction. MIN_vs .

[0102] Figure 8C Including controller supply voltage V ECU The twelfth curve 152, the first line 154 and the second line 156, wherein the first line 154 shows the maximum available voltage V of 13.5V for positive polarity (ie, forward operation) MAX , the second line 156 shows a negative maximum available voltage of -13.5V for negative polarity (ie, reverse operation). MAX (Also known as V MIN ). Figure 8C It is shown that the torque limitation maintains the reference voltage within ±13.5 V, thus demonstrating the effectiveness of the proposed method.

[0103] All three sets of maximum and minimum torque limits from the three constraints of the system are combined using the following equations (21)-(22) to find the final maximum torque τ of the controller MAX_final and the final minimum torque τ MIN_final :

[0104] τ MAX_final = min(τ MAX_im , τ MAX_is , τ MAX_vs) (twenty one)

[0105] τ MIN_final = max(τ MIN_im , τ MIN_is , τ MIN_vs ) (twenty two)

[0106] The equations (23)-(24) below describe the equations executed by the torque limiter 76 to determine the limited torque command τ cmdlim The torque command τ cmd This limitation:

[0107] τ cmd ≥ τ MAX_final ; τ cmdlim = τ MAX_final ;integrator(ω ref – ω) = 0 (23)

[0108] τ cmd ≤ τ MAX_final ; τ cmdlim = τ MIN_final ;integrator(ω ref – ω) = 0 (24)

[0109] Anti-saturation

[0110] Once the torque command signal τ cmd Exceeding these limits (i.e., if the torque command signal τ cmd Greater than the final maximum torque τ MAX_final Or less than the final minimum torque τ MIN_final ), the torque limiter 76 can generate an anti-saturation signal AW, thereby indicating the limited torque command τ cmdlim In response to the anti-saturation signal AW, the integrator 86 may suspend operation. For example, the anti-saturation signal AW may cause the integrator 86 to output a zero signal. Thus, in response to the anti-saturation signal AW, the integrator 86 will stop at the previous value it obtained, and once the system 50 moves out of the anti-saturation region, the integrator 88 resumes operation.

[0111] In some embodiments, the current command i cmd Instead of the actual motor current i, it is used to calculate the brush voltage drop v b For example, if the motor current measurement i m becomes unavailable, you can use the current command i cmd .

[0112] Fig. 9A graph showing the torque produced by the DC motors 26, 28 over a period of time using the disclosed method and two alternative techniques for operating the DC motors 26, 28, each of which includes estimating the brush voltage drop v b .

[0113] Fig. 9 Included is the maximum torque limit τ max The first curve 162 and shows the minimum torque limit τ min The second curve 164 is calculated using the technology of the present disclosure so that the supply current value i s Do not exceed the supply current limit I slim , -I slim . Fig. 9 Also included are a third curve 166 and a fourth curve 168 showing a maximum torque limit and a minimum torque limit, respectively, which are calculated so that the supply current value i s Do not exceed the supply current limit I slim , -I slim , and an alternative technique is used that uses the brush voltage drop v b The simplifying assumption is that is constant. Fig. 9 Also included are a fifth curve 170 and a sixth curve 172 showing a maximum torque limit and a minimum torque limit, respectively, which are calculated so that the supply current value i s Do not exceed the supply current limit I slim , -I slim , and an alternative technique was used that uses an iterative solver.

[0114] Fig. 9 The graph of FIG. 1 shows a positive torque limit (i.e., forward operation) during time 0 seconds to 4.8 seconds, and a negative torque limit (i.e., reverse operation) between about 4.8 seconds and 9.0 seconds. As shown in the figure, during the forward operation from time 0 seconds to 4.8 seconds, when the maximum torque limit τ max When it is a related term, it shows the maximum torque limit τ max The first curve 162 is approximately equal to the corresponding fifth curve 170. Similarly, during the reverse operation (between 4.8 seconds and 9.0 seconds), when the minimum torque limit τ min When the relevant term is min1The second curve 164 is approximately equal to the corresponding sixth curve 172. This demonstrates the effectiveness of the disclosed technique, which is more accurate for generating torque limits to meet operating conditions when compared to the simplified method shown in the third curve 166 and the fourth curve 168, while also using significantly less computing resources than the iterative technique shown in the fifth curve 170 and the sixth curve 172.

[0115] Additionally, the iterative solver technique uses zero for the minimum torque limit during forward operation (between 0 seconds and 4.8 seconds), as shown in the sixth curve 172. The iterative solver technique also uses zero for the maximum torque limit during reverse operation (between 4.8 seconds and 9.0 seconds), as shown in the fifth curve 170. On the other hand, the system and method of the present disclosure do not use zero for the maximum limit or the minimum limit at any time. Therefore, this avoids any possible confusion as to whether the maximum torque limit or the minimum torque limit should be zero at the stationary position. This difference also enables the system and method of the present disclosure to avoid delays in deciding whether to use a zero value, making the method more robust.

[0116] Fig.10 A flow chart listing the steps of a method 200 for operating a DC motor according to various aspects of the present disclosure is shown. The method 200 may be performed by the motor controller 70 of the present disclosure. It will be appreciated from the present disclosure that the order of operations within the method is not limited to the following. Fig.10 Rather, the steps are not performed in the order shown in the drawings, but may be performed in one or more altered orders according to the present disclosure when applicable.

[0117] At 202, method 200 determines a brush voltage drop across a set of brushes of a brushed DC motor based on one of a motor current command or an actual motor current. For example, processor 62 may execute instructions to calculate the brush voltage drop v using equation (3): b , and based on the motor current command i cmd or based on a motor current signal i representing a measured value of the actual motor current i m .

[0118] At 204, method 200 determines at least one of the following based on the brush voltage drop: a first torque limit based on a supply current value not exceeding a supply current limit, and a second torque limit based on a controller supply voltage value not exceeding a maximum available voltage. For example, processor 62 may execute instructions to calculate a maximum torque τ based on the supply current MAX_is 、Minimum torque τ based on supply current MIN_is , Maximum torque τ based on supply voltage MAX_vs , and / or the minimum torque τ based on the supply voltage MIN_vs, and use the corresponding equations in Equation (13), Equation (14), Equation (19) and / or Equation (20).

[0119] At 206, the method 200 determines a final torque limit based on at least one of the first torque limit and the second torque limit. For example, the processor 62 may execute instructions to calculate the final maximum torque τ MAX_final and / or the final minimum torque τ MIN_final , as described in equations (21)-(22).

[0120] At 208, method 200 determines a limited torque command based on the torque command, the limited torque command not exceeding the final torque limit. For example, processor 62 may execute instructions to implement torque limiter 76, which is configured to be based on the torque command signal τ cmd Generate limited torque command τ cmdlim , limited torque command τ cmdlim Not exceeding the final maximum torque τ MAX_final and / or the final minimum torque τ MIN _f i na l .

[0121] At 210 , the method 200 determines a voltage command based on the limited torque command. For example, the processor 62 may execute instructions to implement the torque regulator 78 and the current regulator 80 , wherein the torque regulator 78 is based on the limited torque command τ cmdlim To generate the current command i cmd , and wherein the current regulator 80 is based on the current command i cmd To generate the voltage command v cmd .

[0122] At 212, method 200 applies a DC voltage to the brushed DC motor based on the voltage command. For example, voltage regulator 52 may generate a DC voltage v and apply the DC voltage v to the first brush 30 of DC motor 26, 28, wherein the DC voltage v is based on the voltage command v from controller 60. cmd .

[0123] The present disclosure provides a method for controlling a brushed DC motor. The method includes: determining a brush voltage drop on a set of brushes of a brushed DC motor based on one of a motor current command or an actual motor current; determining at least one of the following based on the brush voltage drop: a first torque limit based on a supply current value not exceeding a supply current limit, and a second torque limit based on a controller supply voltage value not exceeding a maximum available voltage; determining a final torque limit based on at least one of the first torque limit and the second torque limit; determining a limited torque command based on a torque command and not exceeding the final torque limit; determining a voltage command based on the limited torque command; and applying a DC voltage to the brushed DC motor based on the voltage command.

[0124] In some embodiments, determining the brush voltage drop includes determining the brush voltage drop according to the nonlinear equation v b =sign(i)* To calculate the brush voltage drop, where v b is the brush voltage drop, i is the motor current command or the actual motor current, V 0 is the brush voltage parameter, I 0 is the brush current parameter.

[0125] In some embodiments, the final torque limit is based on the first torque limit.

[0126] In some embodiments, determining the final torque limit includes calculating the first torque limit based on at least one of: The maximum torque limit (τ MAX ), or, according to The minimum torque limit (τ MIN ), where K is the back electromotive force constant of the brushed DC motor, R is the winding resistance of the brushed DC motor, ω is the speed of the brushed DC motor, and v b is the brush voltage drop across a set of brushes in a brushed DC motor, V ECU is the controller supply voltage, I slim is the supply current limit, R c is the controller resistance.

[0127] In some embodiments, the final torque limit is based on the second torque limit.

[0128] In some embodiments, determining the final torque limit includes calculating the second torque limit based on at least one of: The maximum torque limit (τ MAX ), or, according to The minimum torque limit (τ MIN), where K is the back electromotive force constant of the brushed DC motor, R is the winding resistance of the brushed DC motor, V max is the maximum available voltage, ω is the speed of the brushless DC motor, v b It is the brush voltage drop across a set of brushes in a brushed DC motor.

[0129] In some embodiments, the method further includes determining a third torque limit based on the motor current not exceeding a maximum motor current value, and determining the final torque limit further based on the third torque limit.

[0130] In some embodiments, the method further includes integrating a value used to determine the torque command; and suspending integration of the value in response to setting the limited torque command based on the final torque limit.

[0131] In some embodiments, determining the torque limit includes: determining a first maximum torque limit based on a supply current value not exceeding a supply current limit; determining a second maximum torque limit based on a controller supply voltage value not exceeding a maximum available voltage; determining a final maximum torque limit based on a lowest one of a plurality of maximum torque limits including at least the first maximum torque limit and the second maximum torque limit; determining a first minimum torque limit based on a supply current value not exceeding the supply current limit; determining a second minimum torque limit based on a controller supply voltage value not exceeding a maximum available voltage value; and determining a final minimum torque limit based on a highest one of a plurality of minimum torque limits including at least the first minimum torque limit and the second minimum torque limit. The final torque limit may include each of the final maximum torque limit and the final minimum torque limit.

[0132] In some embodiments, the brushed DC motor is an actuator motor configured to control the position of a hand wheel of a steering system in a vehicle.

[0133] The present disclosure provides a motor control system. The motor system includes: a brushed DC motor having a set of brushes; a voltage regulator configured to apply a DC voltage to the brushed DC motor based on a voltage command; and a controller configured to: determine a brush voltage drop across a set of brushes of the brushed DC motor based on one of a motor current command or an actual motor current; determine at least one of the following based on the brush voltage drop: a first torque limit based on a supply current value not exceeding a supply current limit, and a second torque limit based on a controller supply voltage value not exceeding a maximum available voltage; determine a final torque limit based on at least one of the first torque limit and the second torque limit; determine a limited torque command based on the torque command and not exceeding the final torque limit; determine a voltage command based on the limited torque command; and transmit the voltage command to the voltage regulator.

[0134] In some embodiments, determining the brush voltage drop includes determining the brush voltage drop based on To calculate the brush voltage drop, where v b is the brush voltage drop, i is the motor current command or the actual motor current, V 0 is the brush voltage parameter, I 0 is the brush current parameter.

[0135] In some embodiments, the final torque limit is based on the first torque limit.

[0136] In some embodiments, determining the final torque limit includes calculating the first torque limit based on at least one of: The maximum torque limit (Τ MAX ), or, according to The minimum torque limit (τ MIN ), where K is the back electromotive force constant of the brushed DC motor, R is the winding resistance of the brushed DC motor, ω is the speed of the brushed DC motor, and v b is the brush voltage drop across a set of brushes in a brushed DC motor, V ECU is the controller supply voltage, I slim is the supply current limit, R c is the controller resistance.

[0137] In some embodiments, the final torque limit is based on the second torque limit.

[0138] In some embodiments, determining the final torque limit includes calculating the second torque limit based on at least one of: The maximum torque limit (Τ MAX ), or, according to The minimum torque limit (Τ MIN ), where K is the back electromotive force constant of the brushed DC motor, R is the winding resistance of the brushed DC motor, V MAX is the maximum available voltage, ω is the speed of the brushless DC motor, v b It is the brush voltage drop across a set of brushes in a brushed DC motor.

[0139] In some embodiments, the controller is further configured to determine a third torque limit based on the motor current not exceeding a maximum motor current value, and to determine the final torque limit further based on the third torque limit.

[0140] In some embodiments, the controller is further configured to: integrate a value used to determine the torque command; and suspend integration of the value in response to setting the limited torque command based on the final torque limit.

[0141] In some embodiments, determining the torque limit includes: determining a first maximum torque limit based on a supply current value not exceeding a supply current limit; determining a second maximum torque limit based on a controller supply voltage value not exceeding a maximum available voltage; determining a final maximum torque limit based on a lowest one of a plurality of maximum torque limits including at least the first maximum torque limit and the second maximum torque limit; determining a first minimum torque limit based on a supply current value not exceeding the supply current limit; determining a second minimum torque limit based on a controller supply voltage value not exceeding a maximum available voltage value; and determining a final minimum torque limit based on a highest one of a plurality of minimum torque limits including at least the first minimum torque limit and the second minimum torque limit. The final torque limit may include each of the final maximum torque limit and the final minimum torque limit.

[0142] In some embodiments, the brushed DC motor is an actuator motor configured to control the position of a hand wheel of a steering system in a vehicle.

[0143] Although the present disclosure has been described in detail in conjunction with only a limited number of embodiments, it should be readily understood that the present disclosure is not limited to these disclosed embodiments. On the contrary, the present disclosure may be modified to encompass any number of changes, modifications, permutations, or equivalent arrangements not previously described but commensurate with the scope of the present disclosure. Additionally, although various embodiments of the present disclosure have been described, it should be understood that various aspects of the present disclosure may include only some of the described embodiments or a combination of various embodiments. Therefore, the present disclosure should not be considered to be limited by the foregoing description.

Claims

1. A method for controlling a brushed DC motor, comprising: determining a brush voltage drop across a set of brushes of the brushed DC motor based on one of a motor current command or an actual motor current; determining, based on the brush voltage drop, at least one of: a first torque limit based on a supply current value not exceeding a supply current limit, and a second torque limit based on a controller supply voltage value not exceeding a maximum available voltage; determining a final torque limit based on at least one of the first torque limit and the second torque limit; determining a limited torque command based on the torque command and not exceeding the final torque limit; determining a voltage command based on the limited torque command; and A DC voltage is applied to the brushed DC motor based on the voltage command.

2. The method according to claim 1, wherein: Determining the brush voltage drop includes using the nonlinear equation To calculate the brush voltage drop, where v b is the brush voltage drop, i is one of the motor current command or the actual motor current, V0 is a brush voltage parameter, and I0 is a brush current parameter.

3. The method according to claim 1, wherein: The final torque limit is based on the first torque limit.

4. The method according to claim 3, wherein: Determining the final torque limit includes calculating the first torque limit based on at least one of: The maximum torque limit (τ MAX ), or, according to The minimum torque limit (τ MIN ), Where K is the back electromotive force constant of the brushed DC motor, R is the winding resistance of the brushed DC motor, ω is the speed of the brushed DC motor, and v b is the brush voltage drop across a set of brushes of the brushed DC motor, V ECU is the controller supply voltage, I slim is the supply current limit, R c is the controller resistance.

5. The method according to claim 1, wherein: The final torque limit is based on the second torque limit.

6. The method according to claim 5, wherein: Determining the final torque limit includes calculating the second torque limit based on at least one of: The maximum torque limit (τ MAX ), or, according to The minimum torque limit (τ MIN ), Where, K is the back electromotive force constant of the brushed DC motor, R is the winding resistance of the brushed DC motor, V MAX is the maximum available voltage value, ω is the speed of the brushed DC motor, v b is the brush voltage drop across a set of brushes of the brushed DC motor.

7. The method according to claim 1, further comprising: The third torque limit is determined based on the motor current not exceeding the maximum motor current value, and Wherein, the final torque limit is further determined based on the third torque limit.

8. The method according to claim 1, further comprising: integrating a value used to determine the torque command; as well as Integrating the value is suspended in response to the limited torque command being set based on the final torque limit.

9. The method according to claim 1, wherein: Determining the torque limit includes: determining a first maximum torque limit based on the supply current value not exceeding the supply current limit; determining a second maximum torque limit based on the controller supply voltage value not exceeding the maximum available voltage; determining a final maximum torque limit based on a lowest one of a plurality of maximum torque limits including at least the first maximum torque limit and the second maximum torque limit; determining a first minimum torque limit based on the supply current value not exceeding the supply current limit; determining a second minimum torque limit based on the controller supply voltage value not exceeding the maximum available voltage value; and determining a final minimum torque limit based on a highest one of a plurality of minimum torque limits including at least the first minimum torque limit and the second minimum torque limit, and The final torque limit includes each of the final maximum torque limit and the final minimum torque limit.

10. The method according to claim 1, wherein: The brushed DC motor is an actuator motor configured to control the position of a hand wheel of a steering system in a vehicle.

11. A motor control system, comprising: A brushed DC motor, wherein the brushed DC motor has a set of brushes; a voltage regulator configured to apply a DC voltage to the brushed DC motor based on a voltage command; as well as The controller is configured as: determining a brush voltage drop across a set of brushes of the brushed DC motor based on one of a motor current command or an actual motor current; determining, based on the brush voltage drop, at least one of: a first torque limit based on a supply current value not exceeding a supply current limit, and a second torque limit based on a controller supply voltage value not exceeding a maximum available voltage; determining a final torque limit based on at least one of the first torque limit and the second torque limit; determining a limited torque command based on the torque command and not exceeding the final torque limit; determining a voltage command based on the limited torque command; and The voltage command is transmitted to the voltage regulator.

12. The system according to claim 11, wherein: Determining the brush voltage drop includes based on To calculate the brush voltage drop, where v b is the brush voltage drop, i is one of the motor current command or the actual motor current, V0 is a brush voltage parameter, and I0 is a brush current parameter.

13. The system according to claim 11, wherein: The final torque limit is based on the first torque limit.

14. The system according to claim 13, wherein: Determining the final torque limit includes calculating the first torque limit based on at least one of: The maximum torque limit (τ MAX ), or, according to The minimum torque limit (τ MIN ), Where K is the back electromotive force constant of the brushed DC motor, R is the winding resistance of the brushed DC motor, ω is the speed of the brushed DC motor, and v b is the brush voltage drop across a set of brushes of the brushed DC motor, V ECU is the controller supply voltage, I slim is the supply current limit, R c is the controller resistance.

15. The system according to claim 11, wherein: The final torque limit is based on the second torque limit.

16. The system of claim 15, wherein: Determining the final torque limit includes calculating the second torque limit based on at least one of: The maximum torque limit (τ MAX ), or, according to The minimum torque limit (τ MIN ), Where, K is the back electromotive force constant of the brushed DC motor, R is the winding resistance of the brushed DC motor, V MAX is the maximum available voltage value, ω is the speed of the brushed DC motor, v b is the brush voltage drop across a set of brushes of the brushed DC motor.

17. The system of claim 11, wherein: The controller is further configured to determine a third torque limit based on the motor current not exceeding a maximum motor current value, and Wherein, the final torque limit is further determined based on the third torque limit.

18. The system of claim 11, wherein: The controller is also configured to: integrating a value used to determine the torque command; and Integrating the value is suspended in response to the limited torque command being set based on the final torque limit.

19. The system of claim 11, wherein: Determining the torque limit includes: determining a first maximum torque limit based on the supply current value not exceeding the supply current limit; determining a second maximum torque limit based on the controller supply voltage value not exceeding the maximum available voltage; determining a final maximum torque limit based on a lowest one of a plurality of maximum torque limits including at least the first maximum torque limit and the second maximum torque limit; determining a first minimum torque limit based on the supply current value not exceeding the supply current limit; determining a second minimum torque limit based on the controller supply voltage value not exceeding the maximum available voltage value; and determining a final minimum torque limit based on a highest one of a plurality of minimum torque limits including at least the first minimum torque limit and the second minimum torque limit, and The final torque limit includes each of the final maximum torque limit and the final minimum torque limit.

20. The system of claim 11, wherein: The brushed DC motor is an actuator motor configured to control the position of a hand wheel of a steering system in a vehicle.

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