Haptic aircraft control device and associated method for controlling at least one motor of the haptic device

Abstract

This method for controlling the motor of an aircraft control system, the system comprising a control stick connected by a mechanical linkage to a motor shaft, includes successive steps of: determining a stiffness setpoint and a damping setpoint to be applied to the stick; determining a required torque setpoint from the stiffness and damping setpoints; controlling the motor to generate the required torque based on the required torque setpoint; and providing feedback based on a first angular position (θs) of the stick from a first angular position sensor and based on a second angular position of the motor shaft from a second angular position sensor. The method is implemented using internal (203), external (202), and current (201) loops, the internal loop (203) being equipped with a controller (Kp) representing either a proportional gain or an integral proportional gain.Figure for the abbreviation: Figure 4.

Description

Title of the invention: Haptic aircraft control device and associated method for controlling at least one motor of the haptic device technical field

[0001] The field of the invention is that of aircraft control devices. More particularly, the invention relates to control devices comprising a joystick with force feedback that allows for the reproduction or simulation of an artificial force felt by the user via the joystick. Prior art

[0002] An aircraft control device generally includes a control stick mounted to rotate about a so-called roll axis and a so-called pitch axis, these two axes being orthogonal to each other.

[0003] Depending on the position of the control stick along the two axes, the aircraft control device transmits movement commands to aircraft piloting instruments.

[0004] A force feedback control device, or force feedback haptic device, is a device configured to generate an artificial force felt by the user, which opposes the movement applied by the user's hand.

[0005] Such a control device is part of an aircraft's flight control system. The control is performed by the user or pilot by moving the control stick, generally rotating it, around an axis fixed to a support.

[0006] The feedback via the joystick is generally achieved by a motor connected to the joystick, to apply an artificial force. This artificial force is obtained by a torque generated by the motor on the joystick. This artificial force allows for the restoration of stiffness and / or damping. The intensity of the artificial force to be applied is determined according to an angular position of the motor used to control the joystick, measured by a position sensor located on the motor shaft.

[0007] State-of-the-art control devices have certain limitations depending on the operating mode. For example, in forced mode, i.e., when the user manipulates the control stick to control the aircraft, the mechanical play and physical stiffness of the stick lead to inaccuracies in the force felt by the user. In free mode, i.e., when the pilot releases the control stick, the servo system aims to return the stick to its anchored position with a significant static error due to dry friction. Description of the invention

[0008] The present invention aims to provide a joystick control solution with improved precision.

[0009] The invention relates to a method of controlling at least one motor of an aircraft control device, the device comprising an aircraft control stick, the stick being connected by a mechanical link to a motor shaft.

[0010] The process comprises successive steps of: - determination of a stiffness setpoint and a damping setpoint to be applied to the handle; - determination of a required torque setpoint from the stiffness and damping setpoints; - control of the motor to generate the required torque based on the required torque setpoint; - feedback based on a first angular position of the joystick from a first angular position sensor and based on a second angular position of the motor shaft from a second angular position sensor.

[0011] The method is implemented by an inner loop, an outer loop and a current loop, the inner loop being equipped with a corrector representing either a proportional gain or an integral proportional gain.

[0012] The use of an inner loop, in addition to the outer loop and the current loop, makes it possible to improve the accuracy of such a process.

[0013] Advantageously, the stiffness setpoint is determined by the formula: KPapp^^k(A +

[0014] where:

[0015] Kp is the inner loop corrector,

[0016] k is a predetermined parameter representing the stiffness of the mechanical link connecting the motor and the joystick, expressed in Nm / rad, and

[0017] A is a position corrector implemented in the outer loop, dimensionless.

[0018] Such a process makes it easy to obtain an apparent stiffness higher than the stiffness of the mechanical link connecting the motor and the handle.

[0019] According to a first embodiment, the inner loop controller represents a proportional gain and the position controller A is a unity gain, and the stiffness setpoint is determined by the formula:

[0020] Kn APapp~ £KP+k

[0021] and the depreciation (Kvapp) by the formula: 2K],f +[(Kr + (k-Kp) KVaPP = (Kr + kf

[0022] where:

[0023] f is a predetermined parameter representing the internal friction coefficient of the mechanical connection, expressed in Nm / rad, and

[0024] fmot is a predetermined parameter representing the internal friction coefficient of the motor, expressed in Nm / rad.

[0025] According to a second embodiment, the inner loop controller represents an integral proportional gain and the stiffness setpoint is determined by the formula:

[0026] Kpapp-k(A + 1) ,

[0027] where A is a dimensionless position corrector.

[0028] For example, the position corrector implements a function according to the formula: ~ " 1

[0029] where:

[0030] f ( 9s ) is a predetermined effort law.

[0031] According to another aspect, the invention relates to an aircraft control device. The device comprises a joystick, a motor including a shaft and a stator, the shaft being rotatably mounted within the stator, and a processing unit. The shaft is connected to the joystick by a mechanical linkage, the joystick being configured to control the aircraft, and the processing unit being configured to implement a control method as defined above.

[0032] Preferably, the control device further includes first and second angular position sensors configured to measure an angular position of the joystick and the motor respectively.

[0033] According to another aspect, the invention relates to a control system for at least one motor of an aircraft control device. The device comprises a current loop, an outer loop and an inner loop and is configured to implement a control method as defined above.

[0034] According to another aspect, the invention relates to an aircraft comprising a control device and a control system as defined above. Brief description of the drawings

[0035] Other objects, features and advantages of the invention will become apparent from the following description, given solely by way of non-limiting example, and made with reference to the accompanying drawings in which:

[0036] [Fig.1] illustrates an aircraft control device according to an example of an embodiment of the invention;

[0037] [Fig.2] is a kinematic diagram of the control device of the [Fig.1];

[0038] [Fig.3] is a flowchart of a control process according to an example of realization of the invention;

[0039] [Fig.4] represents a servo control scheme using the control device of the [Fig. 1]; and

[0040] [Fig.5] illustrates the diagram of [Fig.4] without a so-called "current" loop; Detailed description of at least one embodiment

[0041] Figure 1 shows a control device 1 according to an embodiment of the invention. The control device 1 comprises a joystick 2 mounted for rotation about a roll axis and a pitch axis, these two axes being orthogonal to each other. For simplicity, only one of these axes is shown in Figure 1.

[0042] For each of these two axes the control device 1 includes a motor 3, a first sensor 4 for the angular position of the joystick 2, a second sensor 5 for the angular position of the motor 3 and a third sensor 6 for the intensity of an electric current supplied to the motor 3.

[0043] The motor 3 and the first, second, and third sensors 4, 5, 6 are similar for both axes. The following will describe the operation of the control device 1 along a single axis, referenced AL. The operation on the other axis is identical.

[0044] The control device 1 also includes a processing unit 7.

[0045] The motor 3 comprises a shaft or rotor and a stator. The shaft and the stator are coaxial. For simplicity, we will use the expression angular position of motor 3 to designate the angular position of the shaft relative to the stator.

[0046] The first angular position sensor 4 of the joystick 2 is configured to determine an angular position of the joystick 2 with respect to the AL axis

[0047] The second angular position sensor 5 of the motor 3 is configured to determine an angular position of the motor 3, and it is coupled directly onto the shaft of the motor 3.

[0048] The handle 2 and the motor 3 are connected to each other by a mechanical linkage 8. More precisely, the shaft of the motor 3 is connected to the mechanical linkage 8 which is connected to the handle 2.

[0049] The mechanical link 8 has a reduction ratio R. From the reduction ratio R it is understood that when the motor 3 and more particularly its shaft rotates by an angle a, then the handle 2 rotates by an angle a / R.

[0050] The reduction ratio R can vary non-linearly depending on the angular position of the motor 3. In this case, R represents its linearized value around a given angle α

[0051] The processing unit 7 is configured to receive from the first and second sensors 4, 5 the angular position respectively of the handle 2 and the motor 3. The processing unit is configured to receive from the third sensor 6 the intensity of the electric current measured on the electrical terminals of the motor 3. The processing unit 7 is configured to drive the motor 3 with current based on the setpoints of a current which depends on the force to be applied.

[0052] Figure 2 is a diagram illustrating a kinematic chain of the control device 1 according to the invention. Figure 2 highlights the transmission of torques through the kinematic chain as a function of the reduction ratios and the physical characteristics of inertia, friction, and stiffness of the various components of the kinematic chain.

[0053] On [Fig.2]:

[0054] Jmot designates the moment of inertia of the motor 3 with respect to its axis of rotation;

[0055] fmot denotes the viscous friction coefficient of motor 3,

[0056] JR designates the moment of inertia of the reduction stage with respect to the axis of rotation of the "output" pinion;

[0057] Js designates the moment of inertia of the output axis with respect to its axis of rotation, this inertia may also include that of the lever actuated by the pilot;

[0058] R denotes the reduction ratio of the mechanical link 8;

[0059] ks designates the stiffness of the safety pin located between the gears and the reducer of the mechanical link 8;

[0060] fs denotes the structural viscous friction coefficient of the mechanical link 8 between the output shaft and the reducer;

[0061] Cmi designates the electromagnetic torque applied to the shaft of motor 3;

[0062] C denotes the torque applied to the output shaft by the mechanical chain; and

[0063] Cp, the external torque applied to the output shaft,

[0064] C, the torque applied by the mechanical chain on the motor shaft 3,

[0065] 0m, the angular position of the motor shaft, measured by the second sensor 5 of angular position of motor 3,

[0066] 0S, the angular position of the output axis, measured by the first sensor 4 of angular position of handle 2, and

[0067] 0M, the angular position of the output pinion of the reduction stage, equal to 0m / R.

[0068] The sum of the inertias of motor 3 and the reduction stage of the mechanical link 8 is expressed by the following relationship:

[0069] j = j + J_; (Eq. 1) J m J word R-^ R

[0070] The diagram in [Fig.2] leads to the following dynamic equations:

[0071] JA = Cm - fmjm + C (Eq. 2A, 2B) jsès = cp+c

[0072] With:

[0073] c= -k(es-eM)-f(es-éM) (Eq.3)

[0074] Sm = Mm (Eq. 4)

[0075] -C / R(Eq.5)

[0076] We also obtain:

[0077] R2JJm = -kOm-(R%M+f)»m + Rke,+ Rf6, + R2Cm (Eq.6A.6B) = kf + ^P

[0078] The following state representation is obtained:

[0079] / (W I 0 k 0 k [RJS 1 Èï-ââ 0 f RJS 0 k RJm 0 k

[0080] By choosing the complex number s = jw, the following transfers are identified: • Transfer of engine torque to the joystick position:

[0081] T __________________________(f»+k)_________________________ (Eq. 8) Cm2(^ JJ„fi2s^JsR2fmt+J^ • Transfer of pilot torque to the stick position:

[0082] __________________(Eq. 9) CP2^ JJmR2S^JsR2f™t+J„^^ • Transfer of motor torque to the position after reduction:

[0083] ___Ry^+fs+k)______________________ (Eq. 10) + J^fmg^Jsk+ J^k + R~f fjp +R2fim,k ) • Transfer of pilot torque to the position after reduction:

[0084] T ______________________________Rjfs+k)__________________________ (Eq. 11) Cp20m + J^f + + R2f +R2f„J ) • The transfer of engine torque to the engine position after reduction:

[0085] rp _ Tcm2o„ (Eq. 12) k Cm2ftM — ^2 • Transfer of pilot torque to the motor position after reduction:

[0086] T (Eq. 13)

[0087] The dynamic model can be represented by the following transfer matrix:

[0088] / eM \ _ / GH \ / CM \ (Eq- 14> \ e J = \ TF / \ cp /

[0089] with the following notations:

[0090] G ^TCmleM(EqA5N)

[0091] H - = TCp2oM (Eq. 15B)

[0092] T =TCm23s(Eq. 15C)

[0093] F - =TCp23g (Eq. 15D)

[0094] The processing unit 7 is configured for the implementation of a control method shown in [Fig.3]. This method allows the motor 3 connected to the joystick 2 to be controlled so that the joystick 2 provides a force that is felt by the user.

[0095] The process continues with a step 102 of determining a stiffness setpoint Kpapp and a damping setpoint Kvapp to be delivered on the handle.

[0096] During step 103 of determining a required torque setpoint, the processing unit 7 determines a required torque setpoint from the stiffness and damping setpoints determined in step 102.

[0097] After step 103 of determining the required torque setpoint, the process continues with a step 104 of controlling the motor 3 so that the motor 3 generates a required torque CM corresponding to the required torque setpoint and representative of the effort felt by the user.

[0098] During the feedback step 105, the processing unit 7 calculates the angular position of the output pinion of the reduction stage and receives the angular position of the joystick 2. As previously stated, the angular positions Bs of the joystick 2 and 6m of the motor 3 are measured respectively by the first sensor 4 and the second sensor 5. The angular position Sm of the output pinion of the reduction stage is calculated by dividing the received value of the angular position Bm of the motor 3 by the reduction ratio R. During the feedback step 105, the method provides closed-loop control of the motor of the control device.

[0099] Figure 4 illustrates an example of a control architecture using the control device of the invention. The control scheme includes a first loop 201, called the "current loop". The first loop 201 allows the electric current delivered to the terminals of the motor 3 to be controlled according to the intensity Imot of the electric current required to generate the required torque.

[0100] The control scheme illustrated in [Fig.4] further includes an external loop 202 and an internal loop 203.

[0101] The outer loop 202 receives the angular position value 0s from the first angular position sensor 4 and controls the servo system through a position corrector A associated with a derived action referenced sB.

[0102] The inner loop 203 receives the angular position value from a measurement made by the second angular position sensor 5 and controls the servo system through a compensator denoted Kp associated with a derivative action referenced sK v.

[0103] It should be noted that the first loop 201 is transparent with respect to the mechanical chain. It thus becomes possible to simplify the servo diagram as illustrated in [Fig.5].

[0104] From the diagram illustrated in [Fig.5] we calculate the transfer functions of the closed loop control system.

[0105] The motor torque at the output of the CM reduction stage is defined according to the following expression:

[0106] CM = Kp (A (9C - 3S) - sB6s + 9C - 0M) - sKv9M (Eq. 16)

[0107] Equation 16 can be rewritten as:

[0108] — KP{A + 1) 9C-Kp(A + sB) 9g- (Kp + sK-A^m (Eq. 17)

[0109] Which allows us to write the following relation:

[0110] [Cm\ {A+ 1) \ „ l(Kp + sKv) Kp(A + sB) \ ( (Eq. \cj~l 0 rc VirU 0 o / U' 18)

[0111] Equation 14 can be rewritten according to the following relation:

[0112] / Uw\ _ / 1+ (kp + sKAg KpÇA+sB^G V1 / (G HUKpfA+l) OW^L^ \ {KP + sKv)TY + KP{A + sB)T] FM 0 1 / 0 19)

[0113] By setting:

[0114] (GBF Hpp'xn + iKp + sKAG Kp(A + sB)G y1 nG H\IKP(A+1) 0\\ W \TBF Fbf)\ (Kp + sKv)T l + Kp(A+sB)T] UT FU 0 LU 20) We therefore have the following closed-loop transfer matrix:

[0115] Hbf / 6c (Eq. 21) \ / \ ^BF ^BF / \ Gp /

[0116] corresponding to the servo diagram of figure 4 and linking the external torque Cp applied by the driver and the output angular position setpoint to the output angular position setpoints of the reduction stage 9m and to the angular position of the output axis 9s.

[0117] Kpapp denotes the setpoint stiffness to be restored at the joystick. Kpapp is equal to the inverse of the static gain of the transfer function Fbf, and is expressed by the following equation:

[0118] —-— ' - 1 lim ( I - I lim ( F ( v 11 i KPapp ■ - / rw ) । - i)

[0119] Thus:

[0120] K . n (Eq.23) KPapp~ K^k fA +

[0121] where:

[0122] Kp is the inner loop compensator, expressed in Nm / rad,

[0123] k is a predetermined parameter representing the stiffness of the mechanical link connecting the motor and the joystick, expressed in Nm / rad, and

[0124] A is the dimensionless position corrector.

[0125] According to a first embodiment, Kp represents a proportional gain, and the position corrector A is a unitary gain.

[0126] We then obtain:

[0127] K _9J±L(Eq.24) ^Papp-~KpYk

[0128] Equation 24 shows that the stiffness felt by the pilot is the combination of two stiffnesses in series, namely the stiffness generated by the engine and the stiffness of the mechanical link between the engine and the control stick.

[0129] Thus, in order for the user to feel a stiffness at the handle whose intensity is equal to Kpapp, the motor must generate an initial force, of the stiffness type, whose intensity is equal to:

[0130] ™Pgpp (Eq. 25) KP~ (2k-KPapp)

[0131] Kvapp denotes the apparent damping setpoint, that is, the damping felt by the pilot at the control stick. Kvapp corresponds to the first-order static gain of the transfer function Fbf.

[0132] The following relationship is valid at low frequencies:

[0133] * KPapp + KV^S (Eq' 26)

[0134]

[0135]

[0136]

[0137]

[0138]

[0139]

[0140]

[0141]

[0142]

[0143]

[0144]

[0145]

[0146]

[0147]

[0148]

[0149]

[0150]

[0151]

[0152]

[0153]

[0154]

[0155]

[0156]

[0157] The apparent depreciation is therefore approximately equal to: Kv«PP = J (- ÆPapp) (Eq- 27) And, exactly equal to: As S approaches 0, we obtain the following expression: Kif + K,k2 + + AK2f + BKpk2 + BKpk - AKpK,k - AKpfJt (Eq. 29) KV“PP~ (Kp + kf Assuming that the corrector A has a unit gain and that B is zero, we obtain: +K^ + - KpK„k - KPf^k (Eq. 30) KVaPP~ (Kp + k^ By grouping the terms, we obtain: IKU^ + f^K^k (Eq. 31 A) KV“PP~ {Kp + ky Thus, in order for the user to feel damping at the handle with an intensity equal to Kvapp, the motor must generate a second force, of the damping type, with an intensity equal to: (K^k^^f (Eq. 31B) Kv = k ' J ^k-KP> According to a second embodiment, Kp represents an integral proportional gain, and the position corrector A is dimensionless. Thus, by choosing g? — +1, the apparent stiffness setpoint is the static component of equation 23 which takes the following form: KPapp^A + o (Eq. 32) Equation 32 allows us to transpose the effort law to be reproduced in the external loop 202 through the corrector A. If we assume that the effort law to be reproduced takes the following form: C = f(6s) (Eq. 33) We can then write the following equation: C = KPapp^ = k(A + (Eq. 34) This is equivalent to the following equation: (A + 1) - (Bq - $3) In order to apply a force law / ( ds ), the function A( 6A implemented by the controller A must follow the following equation:

[0158] The control scheme of [Fig.5] allows the static errors of the inner loop 203 and outer loop 202 to be defined respectively by the following equations:

[0159] Eex' =^-^(Eq. 38)

[0160] = Qc + ô- 0w(Eq. 39)

[0161] The setpoint of the inner loop 203 is 8C + ô.

[0162] Considering an integrator in the inner loop 203, the static error of the control system is zero and we have the following relationship:

[0163] % = ^ + d(Eq.4O)

[0164] In free regime, we have the following relationship in the outer loop 202:

[0165] £«=^-^ = ô(Eq.41)

[0166] Or written in another form:

[0167] ^ = ^-5(Eq. 42)

[0168] From equations 40 and 42, it follows that:

[0169] GM-ds = 25 (Eq. 43)

[0170] If 25 is greater than the mechanical clearance between the handle and the output shaft of the reduction stage, then the mechanical stiffness will tend to reduce the gap between two positions in free-running mode.

Claims

Demands

1. Method of controlling at least one motor (3) of a control device (1) of an aircraft, the device (1) comprising a control stick (2) for piloting the aircraft, the control stick (2) being connected by a mechanical linkage (8) to a shaft of the motor (3), said method being characterized in that it comprises successive steps of: - determining a stiffness setpoint (Kpapp) and a damping setpoint (KPapp) to be delivered on the control stick (2); - determining a required torque setpoint (C^) from the stiffness setpoint (Kp((pp)) and the damping setpoint (Kv«pp);- control of the motor (3) to generate a required torque (CM) from the required torque setpoint (C^), - feedback as a function of a first angular position (0S) of the joystick from a first angular position sensor (4) and as a function of a second angular position (0m) of the shaft of the motor (3) from a second angular position sensor (5), said method being implemented by an inner loop (203), an outer loop (202) and a current loop (201), said inner loop (203) being provided with a compensator (Kp) representing either a proportional gain or an integral proportional gain.;

2. Control method according to claim 1, wherein the stiffness setpoint (Kp) is determined by the formula: KPapp^K^k(A + l) where: k is a predetermined parameter representing the stiffness of the mechanical link connecting the motor and the stick, expressed in Nm / rad, and A is a position corrector implemented in the outer loop (202), dimensionless.

3. A control method according to claim 2, wherein Kp represents a proportional gain and the position corrector (A) is a unit gain, and in which the stiffness setpoint (Kpapp) is determined by the formula: KPapp = 2^k and the damping (Kvapp) by the formula: ^app- (Kp + k)2 where: f is a predetermined parameter representing the internal friction coefficient of the mechanical link, expressed in Nm / rad, and fmot is a predetermined parameter representing the internal friction coefficient of the motor, expressed in Nm / rad.

4. A control method according to claim 2, wherein Kp represents an integral proportional gain and wherein the stiffness setpoint ^Pap^) is determined by the formula: KPapp = k(A + 0

5. Method according to claim 4, wherein the position corrector (A) implements a function (A( 3S) ) according to the formula: A / ü \ PPs) i where: f ( 3$ ) is a predetermined effort law.

6. Aircraft control device, the device comprising: - a joystick (2), - a motor (3) comprising a shaft and a stator, the shaft being rotatably mounted in the stator, and - a processing unit (7), the shaft being connected to the joystick (2) by a mechanical linkage (8), the joystick (2) being configured to control the aircraft, the processing unit (7) being configured to implement a control method according to any one of claims 1 to 5.

7. Control device according to claim 6 further comprising first and second angular position sensors (4, 5) configured to measure an angular position respectively of the joystick (2) and the motor (3).

8. Control system for at least one motor (3) of a control device (1) of an aircraft, said system comprising a current loop (201), an external loop (202) and a loop

9. internal (203) and configured to implement a control method according to any one of claims 1 to 5. Aircraft comprising a control device according to claim 6 or 7 and a control system according to claim 8.

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