CN109941248B - Electric drive-based electric vehicle driving/braking anti-slip control system and method - Google Patents
Electric drive-based electric vehicle driving/braking anti-slip control system and method Download PDFInfo
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Abstract
The invention relates to an electric vehicle driving/braking anti-skid control system and method based on electric transmission. The system comprises a control unit taking a double closed loop based on an electric drive motor as a core, an attachment state detection unit, an attachment parameter estimation unit based on electric parameters, an estimation algorithm unit based on optimal attachment parameters, a PMSM motor, a drive unit and the like. When the vehicle does not slip, the motor double-closed-loop structure only works as a motor torque inner loop, and the outer loop only provides a maximum torque reference for judgment; after the vehicle slips, the attachment state detection unit triggers the outer ring control, the attachment parameter outer ring control outputs a torque command, and the torque command is used as a motor torque closed-loop command to form double closed-loop motor control, so that the electric drive vehicle driving/braking control of the electric system is realized. The invention has important significance for realizing the energy recovery of the full electromagnetic braking of the electric automobile.
Description
Technical Field
The invention relates to the technical field of vehicle stability state detection, in particular to an electric vehicle driving/braking anti-slip control system and method based on electric transmission, which realize real-time detection of electric tire ground attachment stable state and electric vehicle driving/braking anti-slip control.
Background
While the vehicle is prone to slip during braking and while traveling on low adhesion surfaces, energy recuperation braking must ensure vehicle adhesion stability. To maximize energy recovery during braking, it is also desirable to maintain the operating point near the maximum ground attachment condition during braking, i.e., to achieve maximum attachment utilization under current tire-road conditions. This ensures maximum braking strength of the vehicle and maintains braking stability during emergency braking or on wet road surfaces. The method for obtaining the optimal parameters of tire-road surface adhesion is currently mostly based on the realization of control of the current slip ratio and adhesion coefficient.
Electrically driven vehicles have the advantage of fast torque response, bi-directional energy while presenting challenges for depth of braking energy recovery and attachment stability control. The invention provides an electric vehicle driving/braking control system and method based on electric transmission, comprising detection and discrimination based on an adhesion state, an estimation algorithm based on maximum adhesion force, a motor double-closed-loop control structure and the like. The invention can improve the real-time performance of the attachment stability control, lay a theoretical foundation and a realization means for realizing the full braking energy recovery of the vehicle, and has important significance for improving the energy-saving safety performance of the electrically driven vehicle.
Disclosure of Invention
Aiming at the defects existing in the prior art, the invention provides an electric vehicle driving/braking anti-skid control system and method based on electric transmission, which utilize a force transmission factor to detect and judge stability in real time, identify and drive anti-skid control through maximum adhesive force or optimal slip rate, and ensure the safety and stability of vehicle operation.
In order to achieve the above purpose, the invention adopts the following technical scheme:
an electric vehicle driving/braking anti-skid control system based on electric transmission comprises a control unit (1) based on an electric driving motor double closed loop, an attachment state detection unit (2), an electric parameter attachment parameter estimation unit (3), an optimal attachment parameter estimation algorithm unit (4) and a PMSM motor and driving unit (5), and is characterized in that the control unit (1) based on the driving motor double closed loop is connected with the attachment state detection unit (2), the electric parameter attachment parameter estimation unit (3), the optimal attachment parameter estimation algorithm unit (4) and the PMSM motor and driving unit (5), and the attachment state detection unit (2) and the electric parameter attachment parameter estimation unit (3) are respectively connected with the optimal attachment parameter estimation algorithm unit (4) and the PMSM motor and driving unit (5); the actuating unit of driving/braking is PMSM motor and actuating unit (5), the control unit is double closed loop, the inner loop is motor torque closed loop, the outer loop is attachment control taking optimal slip rate or maximum adhesive force as reference; the attachment state detection unit (2) and the attachment parameter estimation unit (3) based on electric parameters jointly act to trigger the maximum attachment force or the optimal slip rate of the feedback vehicle acquired by the estimation algorithm unit (4) based on the optimal attachment parameters, the outer ring controller based on the observed attachment force or slip rate provided by the attachment parameter estimation unit (3) adopts a PI regulator or a control algorithm based on the PI regulator, and therefore driving/braking control of the electric drive vehicle is achieved. The structure is suitable for the electric automobile driven by independent wheels and the electric automobile driven by the centralized driving, and can realize the recovery of braking energy to the greatest extent.
The attachment state detection and discrimination are based on accurate measurement and online estimation of motor parameters, and the calculation method is obtained by detection of force transmission factors.
The calculation method is obtained by an observation algorithm of adhesive force or slip rate based on the electric parameter adhesion parameter estimation, accurate measurement based on motor voltage and current parameters and on-line estimation.
The estimation algorithm based on the optimal adhesion parameters is used for detecting and judging the adhesion state estimated based on the electrical parameters of the motor and optimizing the obtained feedback vehicle maximum adhesion force or optimal slip rate based on the combined action of the electrical parameter adhesion parameter estimation.
The PMSM motor and the drive, the voltage and current information of the motor parameter and the drive unit can be accurately measured, and the powerless platform support is provided for the on-line estimation of the electric drive parameter.
The double closed-loop control structure can introduce feedforward control to improve dynamic response besides the feedback double closed-loop control of the electric driving system. The outer ring controller is a PI regulator, a motor closed-loop engineering design method is used for determining control parameters, and the adhesion reference value is the actual maximum adhesion (or the corresponding optimal slip rate) of the tire-ground.
The control method of the electric vehicle driving/braking anti-skid control system based on electric transmission adopts the system to operate, and comprises the following specific steps:
step S1: measuring armature current I of drive motor a And armature voltage U a Real-time online estimation of adhesion torque T d And a vehicle slip ratio lambda;
step S2: calculating motor output torque variation value DeltaT and adhesion torque variation value DeltaT d Delta T d /ΔT；
Step S3: according to the adhesion torque variation value delta T d The ratio to the output torque variation value DeltaT, deltaT d The delta T force transmission factor judges the adhesion steady state of the automobile tire;
step S4: whether or not to execute the slip prevention control is determined in real time based on the determined steady state of the adhesion of the automobile tire.
Step S5: when the anti-skid control is implemented, an estimation algorithm unit based on the optimal adhesion parameter is triggered on line to acquire the optimal adhesion momentOr an optimal slip rate lambda opt The estimated attachment torque T in step S1 is given as the motor control outer ring d And the vehicle slip rate lambda is used as the feedback quantity of the motor control outer ring attachment control;
step S6: the vehicle attachment controller acts and outputs as
Step S7: based on the driver's desired braking torque T by a decision-making unit drv Calculation ofAs a set of motor torque closed loops;
step S8: and (3) performing closed-loop control on the motor, and further performing anti-skid control on braking.
Compared with the prior art, the invention has the following obvious prominent substantive features and obvious technical progress:
1. the attachment state detection method based on the motor system parameters has the advantages of fewer required sensors, low cost and high reliability.
2. The method for estimating the maximum adhesive force in real time converts the vehicle stability problem with complex relation, disturbance mutation, non-linear and unstable links into the adhesive force control problem, and perfectly solves the problem with a motor double-closed-loop structure.
3. The time constant of the closed loop in the electric vehicle driving/braking anti-skid control based on electric transmission is converted into the electric time constant of the motor, so that the response bandwidth of driving/braking is improved.
Drawings
FIG. 1 is a schematic diagram of a system algorithm unit of the present invention;
FIG. 2 is a schematic diagram of a motor dual closed loop control architecture of the present invention;
FIG. 3 is a flow chart of a drive/brake slip control implementation method of the present invention;
FIG. 4 is a schematic illustration of single wheel longitudinal brake dynamics of the present invention;
FIG. 5 is a schematic graph of vehicle adhesion coefficient versus vehicle slip ratio for the present invention;
FIG. 6 is a graphical representation of the relationship between the ground adhesion coefficient and the vehicle slip ratio for three exemplary road tires of the present invention.
Detailed Description
Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. The drawings are provided only for a better understanding of the invention and they should not be construed as limiting the invention.
Embodiment one: see fig. one to four
The electric vehicle driving/braking anti-skid control system based on electric transmission comprises a control unit (1) based on an electric driving motor double closed loop, an attachment state detection unit (2), an electric parameter attachment parameter estimation unit (3), an optimal attachment parameter estimation algorithm unit (4) and a PMSM motor and driving unit (5), and is characterized in that the control unit (1) based on the driving motor double closed loop is connected with the attachment state detection unit (2), the electric parameter attachment parameter estimation unit (3), the optimal attachment parameter estimation algorithm unit (4) and the PMSM motor and driving unit (5), and the attachment state detection unit (2) and the electric parameter attachment parameter estimation unit (3) are respectively connected with the optimal attachment parameter estimation algorithm unit (4) and the PMSM motor and driving unit (5); the actuating unit of driving/braking is PMSM motor and actuating unit (5), the control unit is double closed loop, the inner loop is motor torque closed loop, the outer loop is attachment control taking optimal slip rate or maximum adhesive force as reference; the attachment state detection unit (2) and the attachment parameter estimation unit (3) based on electric parameters jointly act to trigger the maximum attachment force or the optimal slip rate of the feedback vehicle acquired by the estimation algorithm unit (4) based on the optimal attachment parameters, the outer ring controller based on the observed attachment force or slip rate provided by the attachment parameter estimation unit (3) adopts a PI regulator or a control algorithm based on the PI regulator, and therefore driving/braking control of the electric drive vehicle is achieved. The structure is suitable for the electric automobile driven by independent wheels and the electric automobile driven by the centralized driving, and can realize the recovery of braking energy to the greatest extent.
Embodiment two: substantially the same as the first embodiment, the specific point is that:
the attachment state detection unit (2) is used for detecting and judging the attachment state based on accurate measurement and online estimation of motor parameters, and the calculation method is obtained by detecting the force transmission factors.
The electric parameter-based adhesion parameter estimation unit (3) is based on accurate measurement and online estimation of motor voltage and current parameters, and the calculation method is obtained by an adhesion torque or slip rate observation algorithm.
The optimal adhesion parameter-based estimation algorithm unit (4) is used for acquiring feedback vehicle maximum adhesion torque or optimal slip rate based on the joint triggering action of the adhesion state detection unit (2) estimated by the motor electric parameters and the electric parameter adhesion parameter estimation unit (3).
The PMSM motor and the driving unit (5) can accurately measure the motor parameters and the voltage and current information of the driving unit, and provide a physical platform support for the on-line estimation of the electric driving parameters.
The control structure (1) based on the double closed loops of the electric drive motor can be used for feeding back the double closed loops of the electric drive system and can also be used for introducing feedforward control to improve dynamic response. The outer ring controller is a PI regulator, a motor closed-loop engineering design method is used for determining control parameters, and a reference value for outer ring attachment parameter control is an adjustment torque corresponding to the actual tire-ground maximum attachment torque or an optimal slip ratio corresponding to observation.
Embodiment III: the electric vehicle driving/braking anti-slip control system based on electric transmission is operated by adopting the system, and specifically comprises the following steps:
step S1: measuring armature current I of drive motor a And armature voltage U a Real-time online estimation of adhesion torque T d And a vehicle slip ratio lambda;
step S2: calculating motor output torque variation value DeltaT and adhesion torque variation value DeltaT d Delta T d /ΔT；
Step S3: according to the adhesion torque variation value delta T d The ratio to the output torque variation value DeltaT, deltaT d Determining the adhesion steady state of the automobile tire by the delta T force transmission factor;
step S4: whether or not to execute the slip prevention control is determined in real time based on the determined steady state of the adhesion of the automobile tire.
Step S5: when the anti-skid control is implemented, an estimation algorithm unit based on the optimal adhesion parameter is triggered on line to acquire the optimal adhesion momentOr an optimal slip rate lambda opt The estimated attachment torque T in step S1 is given as the motor control outer ring d And the vehicle slip rate lambda is used as the feedback quantity of the motor control outer ring attachment control;
step S6: the vehicle attachment controller acts and outputs as
Step S7: based on the driver's desired braking torque T by a decision-making unit drv Calculation ofAs a set of motor torque closed loops;
step S8: and (3) performing closed-loop control on the motor, and further performing anti-skid control on braking.
As shown in fig. 1, the electric vehicle driving/braking anti-slip control system based on electric transmission comprises a novel electric vehicle driving/braking anti-slip control method based on electric transmission, which comprises a core control structure (1) based on double closed loops of an electric driving motor, an adhesion state detection unit (2), an electric parameter based adhesion parameter estimation unit (3), an optimal adhesion parameter based estimation algorithm unit (4) and a PMSM motor and driving unit (5).
As shown in fig. 2, the actuating unit of the driving/braking is a PMSM motor and its driving unit (5), the control structure is a double closed loop, the inner loop is a motor torque closed loop, and the outer loop is an adhesion control with reference to an optimal slip ratio or a maximum adhesion force. The feedback of the outer ring is the adhesion or slip ratio. The outer loop controller employs a PI regulator or a control algorithm based thereon. The structure is suitable for the electric automobile driven by independent wheels and the electric automobile driven by the centralized driving, and can realize the recovery of braking energy to the greatest extent.
The closed-loop control of the adhesion (or slip ratio) is characterized in that the adhesion reference value is the actual maximum adhesion (or the corresponding optimal slip ratio) of the tire-ground, and the calculation method is obtained by detecting the force transmission factor. The adhesion state detection is characterized in that the adhesion force or the slip rate measured by the motor parameter detection.
The double closed-loop control structure is characterized in that an outer loop controller is a PI regulator, and a motor closed-loop engineering design method is used for determining control parameters:
the double closed loop control structure is characterized in that feedforward control can be introduced to improve dynamic response besides feedback control.
As shown in fig. 3, the adhesion stability determination method and the maximum adhesion recognition method of the present electrically driven vehicle specifically include the following steps:
step S1: measuring drive motor electricityPivot current I a And armature voltage U a Real-time online estimation of adhesion torque T d And a vehicle slip ratio lambda;
step S2: motor output torque variation value Δt and adhesion torque variation value Δt d Delta T d /ΔT；
Step S3: according to the adhesion torque variation value delta T d The ratio to the output torque variation value DeltaT, deltaT d The delta T force transmission factor judges the adhesion steady state of the automobile tire;
step S4: determining whether to implement anti-skid control in real time according to the determined steady state of the attachment of the automobile tire;
step S5: when the anti-slip control is implemented, the maximum adhesion torque adjustment torque acquired by the estimation algorithm unit based on the optimal adhesion parameter is triggered onlineOr an optimal slip rate lambda opt As a given of the motor control outer ring,
the estimated adhesion torque T in step S1 is processed d And the vehicle slip rate lambda is used as the feedback quantity of the motor control outer ring attachment control;
step S6: the vehicle attachment controller acts and outputs as
Step S7: based on the driver's desired braking torque T by a decision-making unit drv Calculation ofAs a set of motor torque closed loops;
step S8: and (3) performing closed-loop control on the motor, and further performing anti-skid control on braking.
As in the step S1, the driving motor armature current I is measured a And armature voltage U a By measuring with Hall voltage sensor and current sensor, the adhesion torque T is estimated d And a slip ratio lambda. The specific principle is as follows: electric vehicle motors are diverse, but straightThe galvanic machine can reflect the most basic electromechanical characteristics of the motor, has a simple model and is still applied to various vehicle platforms. The invention takes a brush direct current motor model as an example to study the electromechanical characteristics of an electric vehicle. Other types of motors, such as permanent magnet synchronous motors, can be equivalently converted into a direct current motor model through coordinate transformation, and then further analysis and control are performed.
Assuming that the circuit current is continuous, the dynamic voltage equation, back electromotive force EMF equation, electromagnetic torque equation, and electromagnetic time constant equation of the armature circuit can be expressed as:
E a ＝k e ω
T e ＝k t I a
T l ＝L/R
wherein I is a Is armature current, k t Is a torque constant; k (k) e Is the back emf constant; u (U) a Is the armature voltage; r is the armature resistance; l (L) a Is the inductance of the motor; e (E) a Is a back electromotive force; omega is the motor rotation speed; i dL Is the load current; t (T) l Is the armature circuit electromagnetic time constant.
The quarter vehicle model (Quarter Car Model, QCM) (or single wheel model) is a vehicle dynamics model widely used in vehicle traction control research, as shown in fig. 4. The QCM model can obtain a wheel rotation equation and a vehicle motion equation by assuming that the driving force and the adhesive force on the left wheel and the right wheel are equal, wherein T is the driving torque of the wheels, and the driving torque is generated by a motor and transmitted to a wheel shaft through a transmission mechanism to drive the wheels to rotate; j (J) ω Is the equivalent rotational inertia of the wheel; omega is the wheel rotational angular velocity; r is the effective radius of rotation of the wheel; f (F) d Is the friction force generated by the tyre-road surface contact action, also called adhesion force, which is the exciting force for driving the vehicle to move; f (F) dr Is the total resistance to vehicle movement; m is the mass of the whole vehicle; v is the vehicle longitudinal speed.
The tire-road contact action of the drive wheel generates a braking force in the horizontal direction on the vehicle, which is closely related to the slip ratio of the drive wheel. Slip ratio is a dimensionless quantity defined by the formula, representing the degree of differentiation of wheel speed and vehicle speed, epsilon is a small constant to avoid zero denominator.
When the vehicle is braked, the slip rate lambda is less than 0; when the vehicle is towed, the slip rate lambda is more than 0. When λ=0, i.e. the wheel speed ωr is equal to the vehicle body speed V, the wheel is in a pure rolling state; when |λ|=1, the vehicle body speed V at the time of driving is 0 or the wheel speed ωr=0 at the time of braking, the wheels are in a pure sliding state or a completely locked state; when 0 < |lambda| < 1, the wheel speed is unequal to the vehicle body speed and is not zero, and the wheels are in a rolling and sliding state. Friction force, i.e. adhesion force F, generated by tyre-road surface contact d In the formula, mu is the tire-road adhesion coefficient and is related to the longitudinal slip rate lambda; and N is the normal reaction force of the ground to the wheels.
F d ＝μ(λ)
Observations through a number of experimental tests found that: the adhesion coefficient and slip ratio between the tire and the road surface exhibit a non-linear relationship, which may be generally described as shown in fig. 5.
As can be seen from the curve relationship between mu and lambda, mu increases with increasing lambda until reaching the maximum mu max The corresponding slip ratio is called critical slip ratio lambda c . With a further increase in λ, μ will gradually decrease. As can be seen from the relationship of the longitudinal adhesion, when the longitudinal load is unchanged,increasing the slip ratio before the critical slip ratio may increase the adhesion (increase in the adhesion coefficient); at a critical slip ratio operating point, the adhesive force reaches a maximum value; after the critical slip ratio, if the slip ratio is further increased, the adhesion will gradually decrease. The region of the operating point on the mu-lambda curve, which is smaller than the critical slip ratio, is called a stable attachment region; and the operating point region greater than the critical slip ratio is referred to as an unstable slip region; the operating point corresponding to the critical slip ratio is referred to as the optimal operating point.
The wheel-ground relation is a nonlinear model, and is also an unstable link in an unstable region, and when the pole is in the right half plane, the unstable link is adopted, and at the moment, the system is a non-minimum phase system.
Firstly, deriving an observation equation of the adhesion torque based on a vehicle model, a motor model and the like:
the motor speed can be measured by a speed measuring sensor, but the cost and the complexity of the electrical connection are increased, and furthermore, the calculation of the speed differential signal introduces high frequency noise interference. According to the DC motor model equation, the rotating speed signal can be obtained by an observation method based on a motor model:
assuming that the motor is operated in an ideal current closed-loop control state, the first and second orders of the current are approximately zero, so that a novel observation equation of the attachment torque can be obtained, namely
The force transfer function is derived based on the theory of small signal linearization near the working point, and since the mu-lambda curve is nonlinear in nature, i.e. the curve is smooth, single-valued and continuous, the linearization equation shown in the following formula can be obtained by locally linearizing a certain working point.
Δμ＝aΔλ，a＝dμ/dλ
ΔV＝(1-λ)Δωr
ΔF d ＝F z Δμ＝F z ·aΔλ
ΔF dr ＝(a 1 +2a 2 V)ΔV
Deriving the junction of differential equation with the vehicle mathematical model equation and motor basic equation according to the theory can obtain the mathematical expression of the following slip rate observation, namely
Wherein J is ω Is the equivalent rotational inertia of the wheel; r is the effective radius of rotation of the wheel; f (F) dr Is the total resistance to vehicle movement; m is the mass of the whole vehicle; ng is the gear ratio at which the vehicle motor output torque is transferred to the wheels via the retarder and differential.
Adhesion torque T d And the novel observation equation of the slip rate lambda only utilizes the measurement parameters of two variables of motor voltage and current, and the sensors also provide signals for closed-loop control in the motor at the same time, so that the system cost is not additionally increased. In addition, compared with a wheel speed signal, the response bandwidth of the air signal is high, and the measurement accuracy is high.
As in the step S2, the output torque variation Δt and the adhering torque variation Δt are calculated d Wherein the output torque T of the driving motor is obtained by measuring the motor current according to the relation between the current and the output torque, and the output torque T is equal to the torque coefficient and the armature power of the motorFlow product, output torque variation value DeltaT and adhesion torque variation value DeltaT d Respectively representing the output torque T and the wheel attachment torque T transmitted from the motor to the wheels d The deviation value of the results of two successive calculations, i.e. Δt=t (k) -T (k-1), Δt d ＝T d (k)-T d (k-1)。
As in the step S3, according to the adhesion torque variation value DeltaT d The force transmission factor, which is the ratio of the output torque variation value deltat, is used for judging the adhesion steady state of the automobile tire, and comprises the following steps:
when deltat is not equal to 0:
when (when)And->When the vehicle is in a stable attachment state, the vehicle is judged;
when (when)And->When the vehicle is in an unstable slip state, judging that the vehicle is in an unstable slip state;
when (when)And->When the vehicle is in the state of switching from stable adhesion to unstable slip;
when (when)Eye->When the vehicle is in a state of switching from unstable slip to stable adhesion;
at Δt=0:
when DeltaT d (k) > 0 and DeltaT d (k-1) > 0, determining that the vehicle is in a stable adhesion state;
when DeltaT d (k) < 0 and DeltaT d (k-1) when it is less than 0, determining that the vehicle is in an unstable slip state;
when DeltaT d (k) < 0 and DeltaT d (k-1) > 0, determining that the vehicle is in a state of switching from stable adhesion to unstable slip;
when DeltaT d (k) > 0 and DeltaT d (k-1) when it is less than 0, determining that the vehicle is in a state of switching from unstable slip to stable adhesion;
wherein DeltaT d (k) A current calculated adhesion torque variation value; delta T d (k-1) is the adhesion torque variation value calculated at the previous time; deltat (k) is the currently calculated output torque variation value; Δt (k-1) is the output torque variation value calculated at the previous time.
In the step S4, whether to implement the anti-skid control is determined in real time according to the determined steady state of the adhesion of the automobile tire, specifically including: when the vehicle is judged to be in an unstable slip state, a decision unit is triggered to apply anti-slip control to the vehicle driving motor, and when the vehicle is judged to be in a stable attachment state, the anti-slip control is not applied to the vehicle driving motor.
In the step S5, a method for estimating the maximum adhesion in real time comprises the following specific steps:
when the anti-slip control is implemented, an optimal working point is captured according to a force transmission factor judging strategy, and a maximum adhesion parameter estimation criterion corresponding to the optimal working point is as follows:
IF: andt=k-1 when the operating point is stable and andt=k when the operating point is unstable;
THEN: the optimal working point occurs at time period t E (k-1, k); maximum adhesion torque T dmax ≈max{T d (k-1)，T d (k) -a }; (simultaneously optimum slip Rate lambda) opt Can be based on the moment of maximum adhesion torque T dmax Determining corresponding time; ) Then calculateMaximum adhesion torque T dmax Corresponding adjustment torqueAnd (5) standby.
Once the IF condition is triggered, the current tire-road contact condition may be estimated to determine the maximum adhesion torque that the current road condition can provide. On-line triggering of an estimation algorithm unit based on optimal adhesion parameters to obtain maximum adhesion moment adjustment torqueOr an optimal slip rate lambda opt The estimated attachment torque T in step S1 is given as the motor control outer ring d And the vehicle slip ratio lambda as a feedback amount of the motor control outer ring adhesion control.
In practical application, the above-mentioned generation rule can be implemented in the timer interrupt of the embedded controller, and the timer can be set to millisecond level, so that the real-time performance of the identification method can be satisfied.
In the step S6, the outer ring vehicle attachment controller adopts a PI regulator or a control algorithm based thereon, and the vehicle attachment controller acts and outputs asThe controllers employed for the closed loop with optimal slip ratio and the closed loop with maximum adhesion adjustment torque should be separately designed with similarities but not perfect agreement.
In step S7, a decision unit determines a desired braking torque T according to the driver drv Calculation ofAs a set of motor torque closed loops, to the motor control module.
As shown in fig. 2, in the stable attachment state, T dmax Is set equal to the maximum motor drive torque. When the driver drives torque T des Less than T dmax At the time T des Can directly pass through the minimum rotationA torque selector as a motor reference torque signal. Once the working point slightly enters an unstable slip region beyond the transition point, the optimal working point is successfully captured online, and the maximum adhesion torque T under the current tire-road surface contact condition is estimated dmax 。T dmax Is set equal to the maximum attachment torque and limits the motor reference torque signal under the action of the minimum torque selector. Since the motor reference torque is smaller than the maximum adhesion torque of the current tire-road contact, the actually output driving torque does not exceed the maximum adhesion torque of the current tire-road contact under the ideal torque closed-loop control. The working point returns to a stable attachment state, and the slipping phenomenon of the driving wheel can be effectively prevented.
In step S8, the driving/braking control structure is a double closed loop, the inner loop is a motor torque closed loop, the outer loop is an adhesion control with an optimal slip rate or a maximum adhesion corresponding adjustment torque as a reference, and the feedback amount of the outer loop is an observed adhesion torque or slip rate.
Under the condition of no slip, a driver inputs the required torque, a vehicle driving motor follows the closed-loop control output torque given the electromagnetic torque forming the motor, and the vehicle is braked to stably run by transmitting torque through a speed reducer and a differential mechanism.
When the driving given required torque is larger than the maximum adhesion force which can be provided by the road surface, the vehicle enters an unstable adhesion area, at the moment, the adhesion state detection unit triggers the maximum adhesion maintaining torque estimation unit to acquire the maximum adhesion torque, and the decision unit takes control of the driver. According to the closed-loop control of the adhesion parameters of the adhesion torque and the maximum torque of the current road surface estimated in real time, the closed-loop control torque is given as the optimal adhesion torque controller output T ref The decision unit deprives the control right of the driver, and a double closed-loop driving/braking realization structure of the vehicle driving motor is formed at the moment.
When the driver demand torque T drv T less than attachment controller output torque setting ref When that is the case, the decision unit will resume the control of the driver. As shown in FIG. 6, the adhesion coefficient between the vehicle tires and the slip ratio of the vehicle under different road conditionsWhen the vehicle working point enters unstable slip control again, the adhesion control algorithm immediately performs optimal parameter identification, updates the last value, and accordingly achieves control of the maximum adhesion torque under different road conditions.
The foregoing embodiments are only for illustrating the present invention, wherein the structure, connection manner and manufacturing process of each component may be changed, and all equivalent changes and modifications performed on the basis of the technical solution of the present invention should not be excluded from the protection scope of the present invention.
Claims (4)
1. The utility model provides an electric vehicle drive/braking antiskid control system based on electric drive, includes control unit (1) based on electric driving motor double closed loop, adhesion state detecting element (2), based on electric parameter adhesion parameter estimation unit (3), based on the estimation algorithm unit (4) of optimum adhesion parameter and PMSM motor and drive unit (5), its characterized in that:
the electric drive motor double closed loop-based control unit (1) is connected with the attachment state detection unit (2), the electric parameter-based attachment parameter estimation unit (3), the optimal attachment parameter-based estimation algorithm unit (4) and the PMSM motor and drive unit (5), and the attachment state detection unit (2) and the electric parameter-based attachment parameter estimation unit (3) are respectively connected with the optimal attachment parameter-based estimation algorithm unit (4) and the PMSM motor and drive unit (5); the actuating unit of driving/braking is PMSM motor and actuating unit (5), the control unit is double closed loop, the inner loop is motor torque closed loop, the outer loop is attachment control taking optimal slip rate or maximum adhesive force as reference; the attachment state detection unit (2) and the attachment parameter estimation unit (3) based on electric parameters jointly act to trigger the maximum attachment force or the optimal slip rate of the feedback vehicle acquired by the estimation algorithm unit (4) based on the optimal attachment parameters, the outer ring controller based on the observed attachment force or slip rate provided by the attachment parameter estimation unit (3) adopts a PI regulator or a control algorithm based on the PI regulator, and therefore driving/braking control of the electric drive vehicle is achieved; the anti-skid control system is suitable for the electric vehicles driven by independent wheels and the electric vehicles driven by the centralized driving, and realizes braking energy recovery;
the PMSM motor and the driving unit (5) can accurately measure the voltage and current information of the motor parameter and the driving unit, and provide a physical platform support for the on-line estimation of the electric driving parameter;
the control unit (1) based on the double closed loops of the electric drive motor can be used for feeding back the double closed loops of the electric drive system and can also be used for introducing feedforward control to improve dynamic response; the outer ring controller is a PI regulator, a motor closed-loop engineering design method is used for determining control parameters, and a reference value for outer ring attachment parameter control is an adjustment torque corresponding to the actual tire-ground maximum attachment torque or an optimal slip ratio corresponding to observation;
with the electric drive-based electric vehicle drive/brake slip control system, an electric drive-based electric vehicle drive/brake slip control method is performed,
the method comprises the following steps:
step S1: measuring armature current I of drive motor a And armature voltage U a Real-time online estimation of adhesion torque T d And a vehicle slip ratio lambda;
step S2: calculating motor output torque variation value DeltaT and adhesion torque variation value DeltaT d Delta T d /DeltaT; wherein the output torque T of the driving motor is obtained by measuring the motor current and according to the relation between the current and the output torque, the output torque T is equal to the product of the torque coefficient and the armature current of the motor, and the output torque change value delta T and the attachment torque change value delta T d Respectively representing the output torque T and the wheel attachment torque T transmitted from the motor to the wheels d The deviation value of the results of two successive calculations, i.e. Δt=t (k) -T (k-1), Δt d ＝T d (k)-T d (k-1)；
Step S3: according to the adhesion torque variation value delta T d The ratio to the output torque variation value DeltaT, deltaT d The ΔT force transmission factor is used for judging the adhesion steady state of the automobile tire, and comprises the following steps:
at Δt+.0):
when (when)And->When the vehicle is in a stable attachment state, the vehicle is judged;
when (when)And->When the vehicle is in an unstable slip state, judging that the vehicle is in an unstable slip state;
when (when)And->When the vehicle is in the state of switching from stable adhesion to unstable slip;
when (when)And->When the vehicle is in a state of switching from unstable slip to stable adhesion;
at Δt=0:
when DeltaT d (k) > 0 and DeltaT d (k-1) > 0, determining that the vehicle is in a stable adhesion state;
when DeltaT d (k) < 0 and DeltaT d (k-1) when it is less than 0, determining that the vehicle is in an unstable slip state;
when DeltaT d (k) < 0 and DeltaT d (k-1) > 0, determining that the vehicle is in a state of switching from stable adhesion to unstable slip;
when DeltaT d (k) > 0 and DeltaT d When (k-1) < 0, determining that the vehicle is in the unstable stateThe fixed slipping direction is in a stable attachment switching state;
wherein DeltaT d (k) A current calculated adhesion torque variation value; ΔTd (k-1) is the adhesion torque variation value calculated at the previous time; deltat (k) is the currently calculated output torque variation value; delta T (k-1) is the output torque variation value calculated at the previous time;
step S4: determining whether to implement anti-skid control in real time according to the determined steady state of the attachment of the automobile tire; triggering a decision unit to implement anti-slip control on the vehicle driving motor when the vehicle is judged to be in an unstable slip state, and not implementing anti-slip control on the vehicle driving motor when the vehicle is judged to be in a stable attachment state;
step S5: when the anti-skid control is implemented, an estimation algorithm unit based on the optimal adhesion parameter is triggered on line to acquire the optimal adhesion momentOr an optimal slip rate lambda opt The estimated attachment torque T in step S1 is given as the motor control outer ring d And the vehicle slip rate lambda is used as the feedback quantity of the motor control outer ring attachment control;
step S6: the vehicle attachment controller acts and outputs as
Step S7: based on the driver's desired braking torque T by a decision-making unit drv Calculation ofAs a set of motor torque closed loops;
step S8: and performing closed-loop control on the motor, and further performing anti-skid control on braking.
2. The electric vehicle drive/brake slip control system based on electric drive according to claim 1, characterized in that the adhesion state detection unit (2) detects and discriminates the adhesion state based on accurate measurement of motor parameters and on-line estimation, and the calculation method is obtained by detection of force transmission factors.
3. The electric vehicle drive/brake slip control system based on electric drive according to claim 1, characterized in that the electric parameter-based adhesion parameter estimation unit (3) is based on accurate measurement and on-line estimation of motor voltage current parameters, the calculation method of which is obtained by an observation algorithm of adhesion torque or slip ratio.
4. The electric drive-based electric vehicle driving/braking anti-slip control system according to claim 1, wherein the optimal adhesion parameter-based estimation algorithm unit (4) acquires the feedback vehicle maximum adhesion torque or optimal slip ratio based on the co-trigger action of the adhesion state detection unit (2) estimated by the motor and electric appliance parameters and the electric parameter-based adhesion parameter estimation unit (3).
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| US11505176B2 (en) * | 2020-06-30 | 2022-11-22 | Rivian Ip Holdings, Llc | Systems and methods for controlling torque induced yaw in a vehicle |
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