Cockpit sensor system

Abstract

An aircraft feeler system comprising a feeler member (11) arranged to be operated by a user to cause a corresponding movement of a movable aircraft surface, means for detecting the operation of the feeler member by the user and for providing a movement signal associated with the detected operation to a flight control computer, the flight control computer providing a control signal to an actuator to move the aircraft surface in accordance with the movement signal, wherein the means for detecting the operation of the feeler member by the user comprises a force sensor (19) configured to sense a force applied to the feeler member by the user, the movement signal being derived on the basis of the sensed force.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to cockpit feel system for allowing pilot control of an aircraft surface. BACKGROUND

[0002] Various types of cockpit feel systems are known which allow a pilot or crew member to control the movement of a flight control surface, such as a wing flap, a slat, an elevator, a rudder, etc. from the cockpit. The feel system takes the form of a joystick, pedal, lever, handle, wheel, etc. which is operated by the pilot or crew member and, in response to the operation by the crew member, causes the associated flight control surface or surfaces to move as desired.

[0003] Traditional mechanical control systems include mechanical linkages or cables connecting the feel system to the flight surface to transfer movement of the feel system to corresponding movement of the surface. Such systems are still used on some aircraft, particularly smaller aircraft and helicopters.

[0004] More recently, flight feel systems have been developed in which the user detects movement of the feel system by a sensor, or more precisely, by a position sensor which detects the position of the feel system. This provides a position signal to a flight control computer, FCC, which in turn sends an electrical signal to an actuator to move the flight control surface. The algorithm used by the FCC to derive the control signal for the actuator can use a gain factor to vary the gain between the position signal and the control signal, which is an advantage over mechanical systems.

[0005] The movement of the feel system required to move the flight control surface is designed to be as intuitively felt as possible, so, for example, movement of a joystick forward by a certain amount can cause an elevator to rise by a certain amount, further movement forward causes the elevator to move to rise more, movement backwards causes the elevator to lower.

[0006] Even though the actual control is by electrical signals, the user should be able to "feel" that their movement of the feel system is causing movement of the flight control surface, so the feel system is typically designed with springs and optional dampers to provide appropriate force feedback to the user to confirm to them that they are actually controlling the movement. The springs and dampers can be configured so that, for example, as the force to move the member increases, the degree of movement and / or rate of change of position is greater, force sensors can be incorporated in some systems, typically active feel systems, to provide a force level signal / information to the FCC, flight data recorder or any other system.

[0007] The force sensor can have a sensor element that deforms in response to the user's action. The force sensor can for example perform a test flight and provide signals that are useful in automatic actions related to such a feeler. Such a feeler with a force sensor is described for example in US 2013 / 0256463.

[0008] Since the feeler is made of a mechanical part guided by a bearing or bushing, it cannot be completely ruled out that the feeler will stick or jam and, in this case, the force exerted by the user will not cause the desired movement of the feeler which would provide the appropriate position signal to control the flight control surface. In the worst case, the user would then lose control of the surface, which can have catastrophic consequences. The trend towards reduced crew or single-pilot operation, in which a second pilot would have no backup in the event of a failure, is becoming increasingly problematic.

[0009] There is a need for a cockpit feeler system that is able to mitigate the effects of such a jam by adapting to the failure and allowing continued control of the aircraft. SUMMARY

[0010] According to a first aspect of the present disclosure, there is provided an aircraft feeler system comprising: a feeler member arranged to be operated by a user to cause a corresponding movement of a movable aircraft surface; means for detecting the operation of the feeler member by the user and for providing a movement signal associated with the detected operation to a control device, the control device providing a control signal to an actuator to move the aircraft surface in dependence on the movement signal, wherein the means for detecting the operation of the feeler member by the user comprises a force sensor configured to sense a force exerted by the user on the feeler member, the movement signal being derived based on the sensed force.

[0011] Preferably, the control device provides the control signal based on an algorithm that converts a force signal indicative of the sensed force exerted on the feeler by the pilot into a feeler position signal. The algorithm can be executed in the control device itself, or alternatively in some external device or electronic equipment, or alternatively in the electronic equipment of the feeler.

[0012] Preferably, the algorithm converts the force signal into the position signal based on the law of static perception.

[0013] Preferably, the algorithm comprises a stop function defining a limit to the degree to which an increase in force causes a change in the position signal.

[0014] Preferably, the algorithm takes into account the inertia of the sensor system and / or the damping of the sensor system and / or the damping of the sensor system and / or the friction of the sensor system when converting the force signal into a position signal in order to obtain a position signal that accurately represents the actual sensor position regardless of the commanded velocity and acceleration on the grip.

[0015] According to a second aspect, there is provided a method of controlling the movement of a flight control surface of an aircraft, comprising: measuring a force exerted by a user onto a flight sensor member, and deriving a control signal from the measured force; and controlling the movement of the flight control surface in dependence on the control signal. BRIEF DESCRIPTION OF DRAWINGS

[0016] Preferred embodiments will be described, by way of example only, with reference to the accompanying drawings.

[0017] Figure 1 is a schematic view of a known sensor using position sensing.

[0018] Figure 2A and Figure 2B show a front view and a side view, respectively, of a sensor with force sensors.

[0019] Figure 3 is a block diagram of a simple algorithm for a system as described herein.

[0020] Figure 4 is a block diagram of a more complex algorithm for a system as described herein. DETAILED DESCRIPTION

[0021] According to the present disclosure, in the cockpit of an aircraft, one or more flight sensors, such as a joystick, pedals, handles, wheels, etc., are provided within reach of the pilot. The sensors are respectively associated with one or more flight control surfaces of the aircraft that control the flight of the aircraft, such as wing flaps, slats, etc. The pilot is trained to move the sensors in the appropriate direction and to the appropriate extent by their hands and feet to cause the desired movement of the aircraft surfaces. The pilot will develop a feel for the force and displacement to be exerted onto the sensor member to cause any given movement of the corresponding surface, and the pilot will expect to feel resistance when they move the sensor, thereby feeling that they are controlling the movement.

[0022] In a conventional system such as Figure 1 shown, a position sensor 3 will detect the position of the sensor (here a joystick 1) in the side stick unit 2 as it is moved and will generate a corresponding position signal. The position signal is transmitted to a flight control computer FCC (not shown) which performs an algorithm on the position signal, or uses for example a look-up table, to derive a control signal for the actuator to cause the corresponding aircraft surface to move in the desired direction and by the desired amount.

[0023] When the user moves the haptic member 1, the spring and damper (not shown in the middle) create a force sensation, thus making the user "know" that he is controlling the surface (i.e. the user receives force feedback as if the control was a traditional mechanical system). The force sensor 4 can detect the force and provide a force signal / information. Figure 1

[0024] For a given rate of deflection, the amount of force required to move the joystick increases with the amount of deflection due to the spring(s). When a damper is used in the haptic, it also increases with the rate of deflection, typically, it varies linearly with the rate of deflection or the square of the rate of deflection (R2). Due to the mass and inertia of the movable parts of the haptic, the force on the joystick will also vary with the acceleration (rate of change of rate of deflection) applied to the joystick.

[0025] It can then be seen that a given force applied by the crew on the joystick can correspond to an infinite number of joystick positions around the static condition position.

[0026] In the system of the present disclosure, the control device, e.g. an external control computer, such as the FCC or other aircraft electronics, obtains the control signal based on the signal from the force sensor(s) 19 and not from the position sensor(s). The force sensor detects the force applied by the user on the haptic member (here the joystick 11) and produces a corresponding force signal. The FCC (not shown) uses the force signal to obtain a corresponding control signal to move the aircraft surface (not shown). In one embodiment, the algorithm can be performed by electronics in the haptic itself.

[0027] In steady state flight operation (e.g. for a joystick), the grip remains stationary with respect to its support 12 - the force applied by the user on the member will be proportional to its deflection, thus the force signal will be the same as the position signal in a system using position sensors (or with a multiplication factor K). The pilot applies a specific force on the member 11 in a given direction and this causes a corresponding change in the member position. The force sensor 19 essentially produces a control signal in the same way as a position sensor would perform in this case.

[0028] The force sensor 19 can be in the form of a strain gauge, for example, which comprises a diaphragm 20 that flexes according to the amount of torque applied by the pilot on the joystick 11. Other force sensors can also be used, such as magnetostrictive sensors.

[0029] According to the present disclosure, an algorithm is provided to convert the sensed force into a desired position, as Figure 3 ​The detected force signal from force sensor 19 is provided as an input 30 to the algorithm. The algorithm applies a static haptic law 100 to the input, whereby, in general, an increase in force will correspond to a proportional change in position in a given direction. A saturation function is applied to set a stop position beyond which the position will not change with increasing applied force. The algorithm output is a signal indicative of the surface desired position or position change.

[0030] However, to perfectly replicate the conventional joystick operation and feel, the FCC will need to apply a correction factor to the generation of the control signal based on the force signal due to the dampener / spring providing a feedback force. Also, the haptic member itself will have an inherent mass inertia which provides an additional force and G forces can create additional loads on the haptic member. To account for these factors and replicate the control of the current position sensor, a correction factor should be applied to the load used by the FCC to generate the control signal.

[0031] To compensate for this instantaneous force and load, a position or velocity sensor can be provided in the haptic member as well as in the accelerometer. The inertial load is a function of the haptic acceleration and can be calculated from the mass inertia and the associated load and rate of change of rotational speed.

[0032] The "viscous" load generated by the dampener can also be calculated as a function of the joystick speed.

[0033] All of these forces and loads can be considered to calculate a corrected force input signal, for example, using a vector sum of the force sensor signal, the inertial load and the viscous load, to generate a control signal in the FCC that is a true accurate representation of the haptic desired position.

[0034] To account for these factors and provide a more accurate position control, in a preferred embodiment, a more complete algorithm such as Figure 4 is shown. This algorithm includes inertial, damping, friction and stop characteristics. These features are also set to nominal or theoretical values in the algorithm.

[0035] To implement in software, the algorithm is shown in discrete time (i.e. sample time); alternatively, it can also be done in continuous time using analog hardware components.

[0036] In the algorithm, the force output (measured by the force sensor) is subtracted by a number of forces.

[0037] These forces are a friction force (a force dependent on the sign of the displacement direction, the grip speed), a damping force (a force dependent on the grip speed), a static spring force (a force dependent on the grip position), a stop force (a force characteristic when the haptic is forced to a hard stop).

[0038] Any combination of these forces is possible.

[0039] Some of these forces can be optional, e.g. in some cases the friction force can not be taken into account.

[0040] The output of the subtraction represents the force, which is converted into a torque (global torque) taking into account the lever arm / lever radius of the sensor.

[0041] Alternatively, the force sensor can be replaced by a torque sensor; in this case all forces in the proposed algorithm can be replaced by torques. In this case, of course, the radius of the lever arm does not have to be taken into account.

[0042] The global torque is then divided by the inertia of the sensor to obtain the acceleration of the sensor.

[0043] This acceleration is then the input of a first integrator, which outputs the velocity of the sensor. This velocity output is used to calculate the friction force and the damping force. In the example figure, the friction depends on the sign of the velocity, while the damping is proportional to the velocity. In other algorithm implementations, the damping can vary as the square of the velocity or with several slopes, depending on the sensor.

[0044] This velocity is then the input of a second integrator, which outputs the position of the sensor. This position output is used to calculate the static spring force. This static force characteristic can be stored in a lookup table and represents the spring feel of the sensor.

[0045] This position is also used as input for the deadband of the stop, which is set relative to the hard stop position of the sensor. The output of the deadband is the deflection angle caused by the stop stiffness, which is multiplied by the stiffness to obtain the static stop force, and a derivative can also be determined to obtain the stop structure damping (when multiplied by a damping coefficient). The static stop force and the damping force are summed to obtain the stop force.

[0046] Thus, based on the mechanical characteristics of the sensor (inertia, friction, damping, spring, hard stop characteristics), the measured values of the force (or torque) are used to calculate the grip position.

[0047] This estimated position can also be subtracted from the measured position to obtain a position error.

[0048] This position error can be used to detect any abnormal event, such as a broken spring, a missing damper, a stuck sensor. Using Figure 4 An algorithm using some but not all of the features shown in Figure 1 can also be used.

[0049] The algorithm can be executed in a control device that controls the motion of the surface. Alternatively, the algorithm can be executed in an external device or can be executed in the circuit of the sensor.

[0050] In the case of jamming (failure mode), the member will have no or little deflection or change in position when the user applies the same or even more force. If a conventional position sensor is used, no position signal corresponding to the desired movement of the feeler member will be generated, and thus no control signal to move the aircraft surface according to the user's intention will be generated.

[0051] However, with the force sensor of the present disclosure, even in the case of jamming, even if the position does not change or changes less than desired, the system will detect the force applied by the user. If the force sensor is located in the feeler so that it can still measure the force in the event of any jamming, the resulting force signal will be used to generate the control signal. For any jamming condition of the feeler, the force signal will always be a valid input to generate a signal for controlling the movement of the surface.

[0052] The force sensor needs to be located between the grip / lever of the feeler, i.e. the position where the user applies force to the feeler member, and any feeler component that can cause a jamming condition (e.g. bearings, dampers, friction devices, etc.). The closer it is to the grip or lever, the better. Ideally, the force sensor is located in the grip of the grip / lever of the feeler, the user's "feel" will be affected, but he will still be able to safely control the aircraft.

[0053] The arrangement of the present disclosure does not require reconfiguration of existing hardware. The FCC can be designed with a single logic or algorithm to control the flight control surface according to the force signal provided by the feeler member, even in the case of feeler jamming, this logic will remain in control. Alternatively, the algorithm / logic can also be built into an electronic unit dedicated to the feeler or any electronic unit in communication with one or the other of the two mentioned above.

[0054] The described embodiments are merely examples. The scope of the present disclosure is limited only by the claims.

Claims

1. An aircraft susceptor system, comprising: a sensor member (11) arranged to be operated by a user to cause a corresponding movement of a movable aircraft surface; means for detecting the operation of the sensor member by the user and for providing a movement signal associated with the detected operation to a control device which provides a control signal to an actuator to move the aircraft surface in dependence on the movement signal, wherein the means for detecting the operation of the sensor member by the user comprises a force sensor (19) configured to sense a force applied to the sensor member by the user, the movement signal being derived on the basis of the sensed force, wherein the control device provides the control signal on the basis of an algorithm which converts a force signal indicative of the sensed force into a position signal, wherein the inertial load is a function of the sensor member acceleration and can be calculated in dependence on the mass inertia and the associated loads and the rate of change of the rotational speed, and wherein the viscous load generated by the damper can also be calculated in dependence on the joystick speed, wherein the vector sum of the force sensor signal, the inertial load and the viscous load generates a control signal which is a true and accurate representation of the desired position of the sensor member.

2. The system of claim 1, wherein the algorithm converts the force signal into the position signal on the basis of the static law of sensation.

3. The system of claim 1 or 2, wherein the algorithm comprises a deadband function which defines a limit to the extent to which an increase in force causes a change in the position signal.

4. The system of claim 1 or 2, wherein the algorithm takes into account the inertial of the system in converting the force signal into the position signal; and / or wherein the algorithm takes into account the damping of the system in converting the force signal into the position signal; and / or wherein the algorithm takes into account the friction of the system in converting the force signal into the position signal.

5. The system of claim 1 or 2, wherein the control device is a device external to the sensor member (11).

6. The system of claim 1 or 2, further comprising: means whereby the position signal is compared with a measured position signal indicative of the actual position to provide a position error.

7. The system of claim 1 or 2, wherein the algorithm is: within the control device, in a device external to the control device; or executed by circuitry in the sensor member (11).

8. The system of claim 1 or 2, wherein the force sensor is located on the sensor member (11) or in a part of the sensor member (11) which is closer to the part of the sensor member to which the force is applied directly by the user than any part of the sensor member (11) which is capable of generating a stuck condition.

9. The system of claim 1 or 2, wherein the force sensor comprises a strain gauge, or wherein the force sensor comprises a magnetostrictive sensor.

10. A method of controlling the motion of a flight control surface of an aircraft, comprising: measuring a force applied to a flight sensor member by a user and deriving a control signal from the measured force; and controlling movement of the flight control surface in dependence on the control signal, wherein the control signal is derived on the basis of an algorithm which converts a force signal indicative of the sensed force into a position signal, wherein the inertial load is a function of the flight simulator member acceleration and can be calculated from the mass inertia and the associated loads and the rate of change of the rotation speed, and wherein the viscous load generated by the damper can also be calculated from the joystick speed, wherein the vector sum of the force sensor signal, the inertial load and the viscous load generates a control signal that is a true and accurate representation of the flight simulator member desired position.

11. The method of claim 10, wherein the algorithm converts the force signal to the position signal based on a static feel law; and / or wherein the algorithm includes a stop function that defines a limit to the degree to which an increase in force causes a change in the position signal.

12. The method of claim 10 or 11, wherein the algorithm accounts for system inertia and / or system damping and / or system friction in converting the force signal to the position signal.

13. The method of claim 10 or 11, wherein the position signal is compared to a measured position signal indicative of an actual position to provide a position error.

14. The method of claim 10 or 11, wherein the force signal is indicative of a sensed force, the force signal is corrected using the algorithm, a control device uses the corrected force signal to cause movement of the flight control surface, the control device has an architecture that allows the flight control surface to continue to be controlled in the event that the flight simulator member is stuck without the need to reconfigure the logic used by the control device and without the need to use an alternative input signal.

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