JP2013102613A - Electric vehicle control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric vehicle control device that can decide appropriate torque reduction amount which can surely achieve readhesion without need of try and error adjustment.SOLUTION: An electric vehicle control device that controls a main motor of an electric vehicle includes: a slip/skid detector 311 that detects slip/skid of a wheel; a readhesion torque computing unit 312 that outputs the readhesion torque Tref_lim based on a slip acceleration command αsref that is a command value of slip acceleration that is the change rate of speed difference between the wheel and the rail; and a torque command value computing unit 313 that outputs the readhesion torque Tref_lim when detecting the slip/skid, and controls the sliding acceleration.

Description

  The present invention relates to an electric vehicle control apparatus that realizes re-adhesion control that effectively uses adhesive force while maintaining good riding comfort of an electric vehicle.

  An electric vehicle performs acceleration / deceleration by a tangential force (also referred to as adhesive force) between wheels and rails. This tangential force generally shows an example of the slip speed / tangential force coefficient characteristic of FIG. 6 with respect to the slip speed. It has characteristics. The tangential force divided by the axial load (vertical load applied to the rail per wheel axis) is called the tangential force coefficient, and the maximum value of the tangential force coefficient is called the adhesion coefficient. As shown in the figure, the torque that does not exceed the maximum value of the tangential force is the main motor or the air brake force of a dynamic shaft (hereinafter simply referred to as a dynamic shaft) mechanically coupled to the main motor in conjunction with the main motor torque during braking. If it occurs, the car will not run idle and run, and the electric car will travel in the adhesion area with a small sliding speed to the left of the maximum tangential force.

  If a torque larger than the maximum value is generated, the sliding speed increases and the tangential force decreases, so the slipping speed increases and the slipping / sliding state increases.However, when the wheels and rails are dry, the torque or brake generated by the main motor Occasionally, the vehicle performance is set so that the combined value of the air brake force of the dynamic shaft and the main motor torque does not exceed the maximum value of the tangential force, so no idling or sliding occurs. However, as indicated by the solid line, when the rail surface is wet due to rain or the like, the adhesion coefficient decreases and the maximum value of the tangential force becomes smaller than the torque corresponding to the set performance of the vehicle.

  In this case, the slip speed increases and the vehicle is idling / sliding.If left as it is, the tangential force coefficient decreases correspondingly, and the acceleration / deceleration force required for acceleration / deceleration of the vehicle further decreases. It is necessary to detect idling / sliding and reduce the torque generated by the main motor to re-adhere. When re-adhesion is carried out by controlling the torque in this way, the maximum value of the tangential force is maximized as much as possible while suppressing the sliding speed to a small value and the sum of the torque generated by the main motor or the air brake force of the dynamic shaft and the main motor generated torque. It is necessary to increase the acceleration / deceleration performance of the electric vehicle to control the value to be in the vicinity.

  The configuration of a general electric vehicle control device will be described with reference to FIG. FIG. 7 shows a case where four main motors 4 are driven by one electric vehicle control device 3, but individual electric vehicle control devices 3 may be used for each main motor 4. However, since the basic concept of control is the same, the description thereof is omitted.

The master controller 2 outputs the original torque command value Tref0 for acceleration / deceleration based on the operation of the driver.
The re-adhesion controller 31 in the electric vehicle control device 3 normally outputs the original torque command value Tref0 as it is as the torque command value Tref. However, when the idling / sliding is detected, the re-adhesion controller 31 re-adheres the original torque command value Tref0. A value smaller than the value Tref0 is output as the torque command value Tref.
The vector controller 32 in the electric vehicle control device 3 generates a voltage command V corresponding to the torque command value Tref.
The power conversion circuit 33 in the electric vehicle control device 3 applies a voltage corresponding to the voltage command V to the main motor 4.
An angular velocity estimator 34 in the electric vehicle control device 3 estimates the main motor angular velocity Wm from the output voltage / current and the like of the power conversion circuit 33. In some cases, an angular velocity detector is provided in the main motor 4 instead of the angular velocity estimator 34 to measure the main motor angular velocity.

  Next, the operation of the re-adhesion controller 31 will be described with reference to FIG. In addition, the axis acceleration is negative during sliding, but if the absolute value is taken and the brake torque command value is handled as a positive value, it can be handled in the same way as during idling. A case will be described as an example.

  When the torque command value Tref becomes larger than the torque corresponding to the adhesion coefficient at that time, idling occurs (t = t0), and as shown in FIG. 8 (b), the wheel peripheral speed Vw becomes higher than the vehicle body speed Vt. Increases rapidly. When idling is detected (t = t1) and the torque command value Tref is lowered from Tref0 to Tref_lim, the wheel circumferential speed Vw decreases and matches the vehicle body speed Vt (t = t2). At this time, since the idling wheel is re-adhered, the torque command value Tref is increased to a certain value within a short time (t = t3 to t4). After the torque command value Tref is kept constant for a while (t = t4 to t5), it is gradually increased to Tref0 (t = t6). Thereafter, the operation from t = t1 to t6 is repeated.

  Here, the amount of reduction (ΔT = Tref0−Tref_lim) and the reduction time (t2−t1) of the torque command value Tref need to be set to a torque value that can reliably re-adhere the idle wheel.

In Patent Document 1, a tangential force coefficient estimator using a disturbance observer or the like is used to estimate a tangential force between wheels and rails, and when idling or sliding is detected, a torque smaller than the torque corresponding to the estimated value of the tangential force coefficient And a controller that commands a torque corresponding to the estimated value of the tangential force coefficient after returning from the idling or sliding state to the re-adhesion state.
In addition, the method of tangential force estimation by a disturbance observer is described in Non-Patent Document 1, for example.

  The idling / sliding detection method includes a method of detecting from the angular acceleration of the main motor, a method of detecting from the rotational speed difference of a plurality of main motors, and the like. (For example, Non-Patent Document 2)

JP 2002-325307 A

"Application and Evaluation of Speed Sensorless Vector Control / Disturbance Observer and Re-adhesion Control for Real Vehicles" IEICE Transactions D, Vol.124 (2004), No.9, pp.909-916 "Experimental Consideration on Re-adhesion Control of Induction Motor Individually Driven Electric Locomotive" IEEJ Transactions D, Vol.128 (2008), No.1, pp.1-7

Conventionally, it has been difficult to grasp how much the reduction amount ΔT and the reduction time of the torque command value Tref can be re-adhered to the driving wheel.
If the pull-down amount is too small or the pull-down time is too short, the driving wheel cannot be re-adhered. On the other hand, if the pull-down amount is too large or the pull-down time is too long, the acceleration performance and ride comfort are deteriorated. For this reason, it is necessary to make adjustments by changing the amount of reduction and the time for reduction on a trial and error basis, requiring a great deal of time and effort.

  In the case of the method described in Patent Document 1, although it can be reliably re-adhered by lowering the torque to be smaller than the torque corresponding to the tangential force coefficient estimator, how much is appropriate to lower, and what is the lowering time It is difficult to grasp if it is appropriate. Therefore, it is necessary to make a trial and error adjustment in the same manner, and a great deal of time and labor are required.

  Accordingly, an object of the present invention is to provide an electric vehicle control device capable of determining an appropriate torque reduction amount that can reliably realize re-adhesion without performing trial and error adjustment.

  The present invention relates to an idling / sliding detector for detecting idling / sliding of a wheel and a slip acceleration command which is a rate of change of a speed difference between the wheel and the rail in an electric vehicle control device for controlling a main motor of an electric vehicle. A re-adhesion torque calculator that outputs a re-adhesion torque based on a slip acceleration command that is a value, and a torque command value calculator that outputs the re-adhesion torque when slipping / sliding is detected. It is characterized by controlling acceleration.

  The present invention further includes a tangential force coefficient estimator that estimates a tangential force coefficient of a wheel from a main motor angular velocity and a torque command value or a calculated value, and the re-adhesion torque calculator is based on the tangential force coefficient. It is preferable that the re-adhesion torque is output and the slip acceleration is controlled so as to coincide with the slip acceleration command.

  In the present invention, it is preferable that the re-adhesion torque calculator outputs a re-adhesion torque based on a tangential force coefficient at the time of detecting idling / sliding.

  In the present invention, it is preferable that the re-adhesion torque calculator outputs a re-adhesion torque based on a vehicle body acceleration of the electric vehicle.

  The present invention further includes a vehicle body acceleration estimator that estimates vehicle body acceleration and outputs a vehicle body acceleration estimated value, and the re-adhesion torque calculator outputs a re-adhesion torque based on the vehicle body acceleration estimated value, It is preferable to control the sliding acceleration so as to coincide with the sliding acceleration command.

  In the present invention, the vehicle body acceleration estimated value is preferably obtained by delaying the wheel circumferential acceleration converted from the main motor angular velocity.

  According to the present invention, it is possible to determine an appropriate torque reduction amount that can reliably realize re-adhesion without trial and error adjustment.

It is a block diagram which shows 1st Embodiment of the re-adhesion controller of the electric vehicle control apparatus of this invention. It is a block diagram which shows 2nd Embodiment of the re-adhesion controller of the electric vehicle control apparatus of this invention. It is a block diagram which shows 3rd Embodiment of the re-adhesion controller of the electric vehicle control apparatus of this invention. It is a block diagram which shows 4th Embodiment of the re-adhesion controller of the electric vehicle control apparatus of this invention. It is a block diagram which shows an example of a vehicle body acceleration estimator. It is an example of a sliding speed and a tangential force coefficient characteristic. It is an example of the electric vehicle control apparatus by a prior art. It is a figure explaining the behavior at the time of re-adhesion control.

  Hereinafter, an embodiment of an electric vehicle control device of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing a first embodiment of a re-adhesion controller of an electric vehicle control device of the present invention. Since components other than the re-adhesion control of the electric vehicle control device are the same as those in the conventional example described above, the description thereof is omitted.
The re-adhesion controller 31 a according to the first embodiment includes an idling / sliding detector 311, a re-adhesion torque calculator 312, and a torque command calculator 313.

The idling / sliding detector 311 receives the main motor angular velocity Wm detected by a main motor angular velocity estimator (not shown). When the main motor angular velocity Wm exceeds a predetermined threshold, the idling / sliding detector 311 detects the occurrence of idling / sliding and outputs an idling detection signal slip. Further, the idling / sliding detector 311 stops outputting the idling detection signal slip when the main motor angular velocity Wm becomes equal to or less than a predetermined threshold value.
Note that the idling / sliding detector 311 may detect idling / sliding using another method as in Non-Patent Document 1.

The re-adhesion torque calculator 312 receives the sliding acceleration command αsref. The re-adhesion torque calculator 312 calculates the re-adhesion torque Tref_lim based on the sliding acceleration command αsref.
The slip acceleration command αsref is a desired slip acceleration αs, and the slip acceleration αs is a differential value of the slip speed Vs, that is, the inclination of the wheel peripheral speed Vw shown in FIG.

  The torque command calculator 313 receives the original torque command value Tref0, the idling detection signal slip, and the re-adhesion torque Tref_lim. Normally, the torque command calculator 313 outputs the input original torque command value Tref0 as it is as the torque command value Tref. However, when the idling detection signal slip is input, the re-adhesion torque Tref_lim is constant as the torque command value Tref. Time (for example, while the slip detection signal slip is input) is output.

  According to the re-adhesion controller 31a according to the first embodiment of the present invention, it is necessary to perform trial and error adjustment to determine the re-adhesion torque Tref_lim based on the slip acceleration command αsref and to control the slip acceleration αs. Without re-adhesion.

FIG. 2 is a block diagram showing a second embodiment of the re-adhesion controller of the electric vehicle control device of the present invention.
The re-adhesion controller 31 b according to the second embodiment includes a tangential force estimator 314 in addition to the idling / sliding detector 311, the re-adhesion torque calculator 312, and the torque command calculator 313. In the second embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

The tangential force estimator 314 receives the main motor angular velocity Wm and the torque command value Tref. The tangential force estimator 314 estimates and outputs a load torque Test, which is the tangential force between the wheels and the rails as viewed from the main motor side, using a disturbance observer or the like, from the main motor angular velocity Wm and the torque command value Tref. .
Note that the method for estimating the load torque Test by the tangential force estimator 314 is the same as that of the prior art, and thus the description thereof is omitted.
In addition, the tangential force estimator 314 can use the calculated value of the main motor torque using the current detector instead of using the torque command value Tref.

The re-adhesion torque calculator 312 receives the load torque Test, the slip acceleration command αsref [m / s ² ], and the vehicle acceleration αt [m / s ² ] detected by the vehicle acceleration detector (not shown). Is done. The re-adhesion torque calculator 312 calculates the re-adhesion torque Tref_lim [N · m] using equation (1).

Where Rg is the gear ratio (the number of rotations of the main motor / the number of rotations of the wheels), rw [m] is the wheel diameter, and J [kg · m] is the equivalent of the main motor / gear device / axle / wheel as viewed from the main motor. It is moment of inertia.
Equation (1) shows that the amount of torque reduction required to suppress idling can be arbitrarily determined by the slip acceleration command αsref, and the slip acceleration αs can be controlled.

According to the re-adhesion controller 31b according to the second embodiment of the present invention, the re-adhesion torque Tref_lim is determined by the equation (1) using the slip acceleration command αsref, and the slip acceleration αs is controlled. Re-adhesion can be realized reliably without the need for making any adjustments.
Furthermore, by estimating the load torque Test using a disturbance observer etc., it is possible to cope with different tangential forces depending on whether the rail surface is dry or wet due to rain, etc., and more accurate re-adhesion Torque can be calculated.

FIG. 3 is a block diagram showing a third embodiment of the re-adhesion controller of the electric vehicle control device of the present invention.
The re-adhesion controller 31c according to the third embodiment is the same as the re-adhesion controller 31b according to the second embodiment except that the idling detection signal slip is input to the re-adhesion torque calculator 312. The same reference numerals are given to the components, and the description thereof is omitted.

The re-adhesion torque calculator 312 holds the load torque Test input when the slippage detection signal slip is input, and outputs it as the re-adhesion torque Tref_lim.
In the second embodiment described above, the re-adhesion torque calculator 312 calculates the re-adhesion torque Tref_lim using the instantaneous value of the load torque Test, that is, in real time. However, the load torque Test output from the tangential force estimator 314 changes minutely due to vibrations of the gears / drive devices of the electric car and the carriage, and when the load torque Test that changes slightly like this is used. The re-adhesion torque Tref_lim may become unstable.

  According to the re-adhesion controller 31c according to the third embodiment of the present invention, the re-adhesion torque Tref_lim is obtained by using the load torque Test input at the time when the idling detection signal slip is input, so that Tref_lim is not determined. The problem of becoming stable can be avoided.

FIG. 4 is a block diagram showing a fourth embodiment of the re-adhesion controller of the electric vehicle control device of the present invention.
The re-adhesion controller 31d according to the fourth embodiment includes an idling / sliding detector 311, a re-adhesion torque calculator 312, a torque command calculator 313, and a tangential force estimator 314, as well as vehicle acceleration estimation. A container 315. In the fourth embodiment, the same components as those in the first to third embodiments are denoted by the same reference numerals, and the description thereof is omitted.

The vehicle body acceleration estimator 315 receives the main motor angular velocity Wm and the idling detection signal slip. The vehicle body acceleration estimator 315 obtains and outputs a vehicle body acceleration estimated value αt_est as will be described later.
Instead of using the vehicle body acceleration estimator 315, a vehicle body acceleration detector that detects the longitudinal acceleration of the vehicle body may be used as in the second and third embodiments described above. Since it is difficult to detect the longitudinal acceleration, it is preferable to use the vehicle body acceleration estimator 315.

  In obtaining the vehicle body acceleration estimated value αt_est, the following characteristics can be seen by paying attention to the wheel circumferential acceleration αw and the vehicle body acceleration αt during the re-adhesion control in FIG.

  The first feature is that the wheel circumferential acceleration αw and the vehicle body acceleration αt substantially coincide with each other in a state before starting idling (t <t0). Therefore, it is possible to regard the wheel circumferential acceleration αw as the vehicle body acceleration αt.

  The second feature is that the vehicle body acceleration αt hardly changes even when idling occurs (t0 ≦ t). This is because if the re-adhesion control can be performed appropriately, the tangential force hardly decreases. Moreover, since an electric vehicle is normally driven by a plurality of electric vehicle control devices, even if the torque of one electric vehicle control device is reduced, the influence on the longitudinal acceleration of the vehicle body is small.

  From these two characteristics, the wheel circumferential acceleration αw before the start of idling can be used as the vehicle body acceleration estimated value αt_est. Therefore, the vehicle body acceleration estimator 315 can be configured as shown in FIG. That is, the vehicle body acceleration estimator 315 includes a proportional device 3151, a differentiator 3152, and a delay filter 3153.

The main motor angular velocity Wm is integrated by rw / Rg by a proportional device 3151 and converted to a wheel peripheral velocity Vw. The wheel circumferential speed Vw is converted into wheel circumferential acceleration αw by the differentiator 3152. When the slip detection signal slip is input, the delay filter 3153 delays the wheel circumferential acceleration αw and outputs a vehicle body acceleration estimated value αt_est.
Note that the vehicle body acceleration estimated value αt_est can be made to coincide with the vehicle body acceleration αt at the time of idling by setting the delay time by the delay filter 3153 longer than the time required from the idling to the time of detecting idling. Further, when the slip detection signal slip is input, the output of the delay filter 3153 is held, so that it is possible to prevent the influence of slipping and sliding.

Referring to FIG. 4 again, the re-adhesion torque calculator 312 receives the slip detection signal slip, the vehicle body acceleration estimated value αt_est, the load torque Test, and the slip acceleration command αsref [m / s ² ]. The The re-adhesion torque calculator 312 calculates the re-adhesion torque Tref_lim [N · m] using equation (2).

  If the torque of the main motor is generated as in equation (2), the slip acceleration αs can be matched with the slip acceleration command αsref. Hereinafter, this point will be described.

From the equation of motion of Newtonian mechanics, the motion of the rotating body is
Moment of inertia x angular acceleration = torque (force to rotate)
It becomes the relationship. When the rotating part from the main motor to the wheel of the electric car is replaced with one rotating body, the main motor angular velocity Wm, the generated torque Tm of the main motor 4, and the friction force between the wheel and the rail are viewed from the main motor side. Let T be T

という関係になる。ここで車輪周速度Vwは、主電動機角速度Wmと車輪径ｒwと歯車比Rgを用いると、

It becomes the relationship. Here, the wheel peripheral speed Vw is obtained by using the main motor angular speed Wm, the wheel diameter rw and the gear ratio Rg.

という関係になる。速度の微分値が加速度である点と、すべり加速度αsは車輪周加速度αwと車体加速度αtの差であることから、

It becomes the relationship. Since the differential value of speed is acceleration and the slip acceleration αs is the difference between wheel circumferential acceleration αw and vehicle acceleration αt,

と変形でき、これを（３）式に代入すると、

And substituting this into equation (3)

という方程式が得られる。ここで、変数はαt、αs、Tm、Tの４つであるが、負荷トルクTは車輪・レール間の摩擦力に起因するため直接制御できず、車体加速度αtもその結果なので直接の制御はできない。一方、Tmは主電動機の発生トルクのため直接制御可能である。そのため、Tとαtを把握できれば、主電動機トルクTmにより残ったαsを制御できることがわかる。
上述したとおり、負荷トルクTは、接線力推定器３１４を用いてTestとして推定可能であり、車体加速度αtは車体加速度推定器３１５によって車体加速度推定値αt_estとして推定可能である。そこで（６）式のTをTestに、αtをαt_estに置き換えて変形すると、

The following equation is obtained. Here, there are four variables, αt, αs, Tm, and T. However, since the load torque T is caused by the frictional force between the wheels and rails, it cannot be directly controlled, and the vehicle body acceleration αt is also the result. Can not. On the other hand, Tm can be directly controlled because of the torque generated by the main motor. Therefore, if T and αt can be grasped, it can be understood that the remaining αs can be controlled by the main motor torque Tm.
As described above, the load torque T can be estimated as Test using the tangential force estimator 314, and the vehicle body acceleration αt can be estimated as the vehicle body acceleration estimated value αt_est by the vehicle body acceleration estimator 315. Therefore, if T in Equation (6) is replaced with Test and αt is replaced with αt_est,

という式が得られる。（７）式では、Tmとαs以外は決定しており把握可能なため、αsはTmによって自由に変えられる。そこで、希望するαsをαsrefとして指定すると、主電動機トルクTmが

Is obtained. In equation (7), except Tm and αs are determined and can be grasped, αs can be freely changed by Tm. Therefore, if the desired αs is designated as αsref, the main motor torque Tm is

となればすべり加速度αsがすべり加速度指令αsrefに一致することがわかる。
そのため、（２）式の構成によりTref_limを決定し、トルク指令演算器・ベクトル制御器・電力変換回路を経由して主電動機の発生トルクTmがTref_limと一致することにより、すべり加速度αsをすべり加速度指令αsrefに一致させることができる。
ここで、すべり加速度指令αsrefを負の値とすることにより、すべり速度Vsを減少させることができるため、確実に再粘着させることが可能である。また、空転・滑走を検知した際のすべり速度Vsを見積もることにより、どの程度の時間で再粘着できるか予測可能であり、トルク指令演算器３１５がトルクを引き下げる時間を適切に設計できる。

Then, it is understood that the sliding acceleration αs matches the sliding acceleration command αsref.
Therefore, Tref_lim is determined by the configuration of equation (2), and the slip acceleration αs is determined as the slip acceleration αs by the torque Tm generated by the main motor matches Tref_lim via the torque command calculator, vector controller, and power conversion circuit. It can be matched with the command αsref.
Here, by setting the slip acceleration command αsref to a negative value, the slip speed Vs can be reduced, so that it is possible to reliably re-adhere. In addition, by estimating the slip speed Vs at the time of detecting idling / sliding, it is possible to predict how much time can be re-adhered, and the time for the torque command calculator 315 to reduce the torque can be appropriately designed.

According to the re-adhesion controller 31d according to the fourth embodiment of the present invention, the re-adhesion torque Tref_lim is determined by the equation (2) using the sliding acceleration command αsref and the sliding acceleration αs is controlled. Re-adhesion can be realized reliably without the need for making any adjustments.
In addition, by using the vehicle body acceleration estimated value αt_est, it is not necessary to detect the longitudinal acceleration of the actual electric vehicle body, so the re-adhesion torque is calculated without providing an additional device such as a vehicle body acceleration detector. be able to.

  INDUSTRIAL APPLICABILITY The present invention is effective for realizing re-adhesion control that makes effective use of adhesive force while maintaining good riding comfort of electric vehicles.

DESCRIPTION OF SYMBOLS 1 Vehicle 2 Main controller 3 Electric vehicle control device 31 Re-adhesion controller 311 Idling / sliding detector 312 Re-adhesion torque calculator 313 Torque command calculator 314 Tangential force estimator 315 Car body acceleration estimator 3151 Proportional device 3152 Differentiator 3153 Delay filter 32 Vector controller 33 Power conversion circuit 34 Angular velocity estimator 4 Induction motor 5 Gear device 6 Wheel 7 Rail

Claims (6)

In an electric vehicle control device that controls a main motor of an electric vehicle,
An idling / sliding detector for detecting idling / sliding of wheels,
A re-adhesion torque calculator that outputs a re-adhesion torque based on a slip acceleration command that is a command value of a slip acceleration that is a rate of change of a speed difference between the wheel and the rail;
A torque command value calculator that outputs the re-adhesion torque when idle / sliding is detected;
Have
An electric vehicle control device that controls the sliding acceleration. A tangential force coefficient estimator for estimating the tangential force coefficient of the wheel from the main motor angular speed and the torque command value or the calculated value;
2. The electric vehicle according to claim 1, wherein the re-adhesion torque calculator outputs a re-adhesion torque based on the tangential force coefficient and controls the slip acceleration to coincide with the slip acceleration command. Control device.   The electric vehicle control device according to claim 2, wherein the re-adhesion torque calculator outputs a re-adhesion torque based on a tangential force coefficient at the time of detecting idling / sliding.   The electric vehicle control device according to claim 1, wherein the re-adhesion torque calculator outputs a re-adhesion torque based on a vehicle body acceleration of the electric vehicle. A vehicle body acceleration estimator that estimates the vehicle body acceleration and outputs a vehicle body acceleration estimated value;
4. The re-adhesion torque calculator outputs a re-adhesion torque based on the estimated vehicle body acceleration value, and controls the slip acceleration to match the slip acceleration command. An electric vehicle control device according to claim 1. 6. The electric vehicle control device according to claim 5, wherein the vehicle body acceleration estimated value is obtained by delaying wheel circumferential acceleration converted from the main motor angular velocity.

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