Abstract: A system and method for providing variable motion-resisting loads for a side stick controller on an aircraft where the primary resistive load is provided by a mechanical spring mechanism which is augmented or supplemented by an electric servo motor and electric servo motor linkage system.

Abstract: The present invention provides an active control system for coupling the movements of a pair of independently operated manual input devices such as dual flight control sticks operated by a pilot and co-pilot flying an aircraft. Each input device is configured to receive manual input data in the form of angular displacement of the device about one or more rotational axes. The active control system provides desired tactile feedback to an operator who displaces one of the manual input devices in the form of a restorative centering force. If an external system such as an auto-pilot system is engaged, the restorative force may be in a direction necessary to reconcile manual displacement of the input device with a position commanded by the external system, rather than directed toward the center position. The system also acts to reflect manual displacement of each input device as a force applied to the other.

Abstract: A haptic interface system or force feedback system having a magnetically-controllable device that provides resistance forces opposing movement. The magnetically-controllable device is adapted for use with a force feedback computer system to provide force feedback sensations to the system's operator. The magnetically-controllable device contains a magnetically-controllable medium beneficially providing variable resistance forces in proportion to the strength of an applied magnetic field. The system further comprises a controller that executes an interactive program or event, a video display, and a haptic interface device (e.g. joystick, steering wheel) in operable contact with an operator for controlling inputs and responses to the interactive program.

Abstract: A haptic interface system or force feedback system having a magnetically-controllable device that provides resistance forces opposing movement. The magnetically-controllable device is adapted for use with a force feedback computer system to provide force feedback sensations to the system's operator. The magnetically-controllable device contains a magnetically-controllable medium beneficially providing variable resistance forces in proportion to the strength of an applied magnetic field. The system further comprises a computer system that runs an interactive program or event, a video display display, and a haptic interface device (e.g. joystick, steering wheel) in operable contact with an operator for controlling inputs and responses to the interactive program.

Abstract: Trimming process for adapting a first control loop of a controllable, automatically controlled reference system, which is or represents an aircraft, to a second control loop which simulates the reference system, Flying condition values including controlled variables, which are returned in each control loop for the purpose of the control, are detected, and both control loops are acted upon by the same desired input data. In the first process loop, a conversion of the unreturned flying condition values of the airplane model takes place to the values of the corresponding flying condition values of the reference system. The second process loop is provided for the adaptation of the returned condition values of the airplane simulation system to the corresponding condition values of the reference system.

Abstract: Method, apparatus and sensors for directly interfacing a pilot (1) with the aerodynamic state of the surfaces of an aircraft, in particular allowing the direct sensorization of the conditions of the aerodynamic surfaces during the flight. The pilot (1) wears one or several “data suits” (2), for example on the arm, on the trunk, on the face or on the hands. The information on the boundary layer state is detected by a plurality of sensors (3) located on the different aerodynamic surfaces. A body interface (4) comprising a console (5), a multi-channel conditioning unit (6) and a processor (7) for the data acquisition are connected to the data suit (2). The data suit uses tactile sensations to transmit to the pilot, data responsive to critical airflow conditions at the sensors (3). In an aircraft with many aerodynamic surfaces the pilot can detect directly any arising critical condition.

Abstract: A variable gradient control stick force feel adjustment system for use in aircraft is disclosed. A gradient actuator is operationally coupled to at least one spring cartridge assembly in order to move the pivot point of the spring cartridge assembly with respect to the aircraft's directional hardware so that the tension of at least one manual control stick onboard the aircraft can be adjusted. At least one operational parameter input is provided to the gradient actuator from at least one of the aircraft's onboard control devices in order to effect a change in pivot point for the spring cartridge assembly.

Abstract: A device for actuating a controlled member of an aircraft includes an intentional control member for actuation by the pilot, a computer for piloting on the basis of the action of the pilot on the intentional control member, a controlled member actuator for actuating the controlled member under control of the computer and a slaving device for slaving the position of the intentional control member to the position of the controlled member.

Abstract: A flying aid device for a fly-by-wire aircraft which has at least two mechanically independent control columns (M1, M2). The device (1) includes: a system (SO) for detecting multiple control corresponding to simultaneous operation of at least two of the control columns (M1, M2); and informing systems (S1, S2, S3, S4), each of which is associated with one of the control columns (M1, M2) and is intended to generate within the control column (M1, M2), when the detection system (SO) detects multiple control, a tactile sensation that informs a pilot of the aircraft who is operating the control column (M1, M2) of the multiple control.

Abstract: A pilot-operated lever assembly for adjusting control surfaces of an aircraft including a bobweight for creating inertia forces that simulate a force feedback due to aerodynamic forces on the control surfaces. The bobweight effect is variable as a function of airspeed and other operating variables. An actuator for adjusting the geometry of the lever assembly creates a variable bobweight effect. The mass of the actuator acts as a bobweight mass.

Abstract: Herein disclosed is a flight control system comprising a control member, a control surface controllable to assume different angle positions within a control angle range, a transmission linkage provided between the control member and the control surface to transmit the control force from the control member to the control surface, and a power assist actuator associated with the control member and the transmission linkage to control the control surface.

Abstract: The present invention relates to a system for coupling at least two control columns (2A, 2B) of a control device (DC) of a machine, especially an aircraft. The coupling system includes for each of the columns (2A, 2B), at least one operating member (13A, 13B, 14A, 14B) capable of making the column (2A, 2B) tilt about an axis, and a calculation unit (CAL) receiving information relating to the position of tilt of the columns (2A, 2B) and generating, when at least one of the columns (2A, 2B) is operated, tilt commands which are transmitted to the operating member (13A, 13B, 14A, 14B) of the other column (2A, 2B).

Abstract: An control mechanism apparatus is shown which electromechanically actuates a control board of a radio transmitter. The radio transmitter transmits radio signals to a receiver on board a model aircraft for actuating the various parts thereof. The apparatus comprises a base frame for providing a stable platform with a seat mounted at the rear of the base frame. A plurality of controls emulating the controls found in a cockpit of an actual aircraft are mounted to the base frame. A plurality of mechanical linkages are provided which transmit the position of each of the plurality of controls to a corresponding plurality of electrical devices. Each of the corresponding electrical devices is in electrical communication with the control board and the output of each of the electrical devices varies in accordance with the position of the controls. The radio signals are transmitted by the radio transmitter control board and vary in accordance with the electrical output of each of the electrical devices.

Abstract: A system for backdriving the flight deck controllers of a fly-by-wire aircraft that is under autopilot control to provide a pilot with tactile and visual feedback of autopilot activity. The system, distributed between the aircraft primary flight computers and the autopilot flight computer, uses actuators mechanically coupled to each flight deck controller to position the flight deck controller to mimic manual operation of the flight control surfaces. Additionally, the system allows smooth disengagement of the autopilot and transfer of the aircraft to pilot control when the pilot takes control of any flight deck controller by moving it from a backdrive system-commanded position by a predetermined displacement for a predetermined time.

Abstract: A cyclic stick system for a helicopter or other aircraft includes memories for holding minimum and maximum speed values, a comparator for comparing an air speed V1 with the minimum and maximum speed values, a router for selecting either the air speed V1 or a quiescent speed, a subtracter for obtaining a difference between the output of the router and a reference speed, another router for selecting between the difference and a signal representing an orientation of the stick, and a switch for selecting times when the air speed V1 is to be stored as the reference speed. On the basis of the air speed V1 and under the control of the device for retrimming said cyclic stick, the system acts on the motorization of stick in order to confer on the helicopter apparent longitudinal static stability in terms of forces on the cyclic stick so that to accelerate (or decelerate) and maintain a new higher (or lower) speed.

Abstract: A collective detent system is incorporated in combination with the flight control system of a helicopter to enhance vertical takeoff flight operations of the helicopter.

Abstract: A system for backdriving the flight deck controllers of a fly-by-wire aircraft that is under autopilot control to provide a pilot with tactile and visual feedback of autopilot activity. The system, distributed between the aircraft primary flight computers and the autopilot flight computer, uses actuators mechanically coupled to each flight deck controller to position the flight deck controller to mimic manual operation of the flight control surfaces. Additionally, the system allows smooth disengagement of the autopilot and transfer of the aircraft to pilot control when the pilot takes control of any flight deck controller by moving it from a backdrive system-commanded position by a predetermined displacement for a predetermined time.

Abstract: A cyclic stick system for a helicopter includes sensors for measuring at least one parameter representative of the current flight status of the helicopter. In response to the at least one parameter, the cyclic stick system either (1) continuously and automatically recenters the forces on the cyclic stick, thus canceling out the residual static forces, or (2) allows the pilot fully to feel the countering action of the elastic return device on the cyclic stick.

Abstract: A rudder bar system for a helicopter controlled in yaw by acting on the tail rotor or an equivalent device has a capability, as a function of the parameters representative of the current flight status of the helicopter, of either automatically continuously recentering the forces on the rudder bar, which cancels out the residual static forces and gives the pilot a tactile sensation close to that given by a friction-type rudder bar, or allowing the pilot fully to feel the countering action of an elastic return device such as a spring.

Abstract: A control device with a control stick, wherein the control stick is moved by an irreversible actuator controlled by a computer, and the computer controls the position of the actuator and thus the movement of the control stick, and slaves the control column position to the force applied, in accordance with force data, from a force sensor, and position data, from a position sensor, through use of a position vs. force law entered in the computer.

Abstract: The actuation system of the present invention is based upon sensing relatively small delta errors over relative short strokes as opposed to absolute travel error.

Abstract: A hand controller system which provides the proper feel of the hand controller during aircraft operation. In both non-redundant and redundant embodiments, torque, and position measurements are made from the hand controller movements and processed to provide a feedback to a control motor in mechanical connection with the hand controller. The system includes self-monitoring of the motor, as well as the signals provided by the position, and torque sensors. Connections are provided from the hand controller system so that cross-coupling may be provided between the pilot's and copilot's hand controllers.

Abstract: Synthetic friction force algorithms provide simulated static friction forces as well as dynamic friction forces. On either side of a hand-control element reference position a small static friction zone is established. As long as the hand-control element is within this static friction zone, the reference position remains constant and the control element drive motor generates a centering force proportional to the distance of the hand-control element from the reference position; a force urging the hand-control element toward the reference position. When the relative position of the hand-control element reaches or exceeds an edge of the static friction zone, it enters the dynamic friction zone. The motor applies a constant dynamic friction force, urging the hand-control element toward the reference position and the reference position is translated so that the edge of the static friction zone is translated to the current hand-control element position.

Abstract: A control system for an active hand controller, for example, uses a control stick connected to and controlled by a motor. Electronics are provided to control the motor to eliminate oscillations due to motor torque and high gain due to breakout at the control stick when the control stick is at about its null position. Both hardware as well as software implementations can provide position dependent dampening to the control sticks such that when the control stick is located about a null position, a higher rate of dampening is provided than when the control stick is located outside the null position, when a lower rate of dampening is provided. The system provides a stable active hand controller control stick without degraded force and feel characteristics of the system.

Abstract: A helicopter fly-by-wire flight control system (21) includes a model following control system architecture which provides the pilot with maneuvering feel. Maneuvering feel is generated by varying the gain of a rate model (52) in the control system to schedule a constant sidearm controller force per g of load factor currently on the helicopter main rotor. This gain variation works in conjunction with control logic which requires the pilot to apply a nose up pitch command during steep banked turns in order to offset a control system induced downward (pitch) bias of the aircraft nose. The control system induced bias is generated only during steep banked turns, thus allowing the pilot to fly shallow banked coordinated turns without having to apply a nose up pitch command.

Abstract: An apparatus and method for simulating a desired response in accordance with an external applied force. The apparatus includes a member which is responsive to the applied force, an actuator coupled to the member for exerting a torque on the member, a force sensor for detecting the applied force, and a torque sensor for detecting the torque exerted by the actuator. Signals from the force sensor are used to determine the system response based upon a desired relation. The force sensor signals also are used to determine the actual system response based upon the physical characteristics of the apparatus. The detected torque is compared with the desired and the actual system response, and as a result of the comparison the torque exerted by the actuator onto the member is adjusted accordingly so that the member performs the desired system response. The actuator is preferably an electric motor so that the apparatus can simulate any desired response, notwithstanding the physical characteristics of the system.

Abstract: A helicopter collective control stick having a pilot grip positioned by a linkage assembly whose kinematics permits the control stick to occupy a small envelope and to have the pilot grip motion to be about a large radius. Our collective stick includes a biasing member to balance the control stick and linkage in the mid collective position and which provides a force gradient when the control stick is moved from the mid collective or trimmed position. Further, our collective stick is operable in concert with the full authority side arm controller to operate in either a tracking or a command mode.

Abstract: Device for the control of the elements of a machine having a stick (6,7) designed to be activated by one hand of an operator and mounted tilting around at least one axis (X--X) transverse to the stick. The stick is associated with at least one position sensor (17) which deliver an electric signal representing the tilting of the stick around said axis on both sides of a neutral position, the electric signal controlling at least one of the elements of the machine by a calculation device (30). The device also includes at least one torque motor (12,13) associated to said axis (X--X) so that the tilting of the stick (6,70 drives a relative rotation between the rotor and the stator of the torque motor and in that the torque motor is fed by the calculation device (30).

Abstract: A helicopter programmable collective control system includes a motorized collective control stick 2 used in conjunction with a multi-axis control stick 30, with the multi-axis control stick 30 as the default collective controller. A collective control signal processor reads collective input the pilot is giving through one of the two control sticks 2, 30 and provides a motor drive signal 44 (which is dampened to prevent over control) to position the collective control stick 3. The collective control stick position is used to drive the rotor collective pitch actuators 16.

Abstract: A control system for an aircraft or other man-machine system wherein the usual visual feedback system is characterized and is optimally supplemented by a secondary feel oriented feedback arrangement in which input signals are derived from either of two supplementary feedback signal sources and the resulting algorithms characterized mathematically. The disclosure includes several exemplary arrangements of the feedback systems in which some of the input parameters are of selected value. Mathematical characterization of the feedback paths is used.

Abstract: Device for controlling elements of a machine, comprising a stick intended to be actuated by a single hand of an operator and mounted for tilting about at least one axis transversal to said stick, said stick being associated with at least one position sensor and delivering an electric signal representative of tilting of said stick about said axis, on each side of a neutral position, said electric signal controlling at least one actuator which controls at least one of said elements of the machine. This device is characterized in that said stick is mounted for rotation on itself about its longitudinal axis and in that it comprises at least one other position sensor delivering another electric signal representative of rotation of said stick about itself, on each side of a neutral position, said other electric signal controlling at least one other actuator which controls at least one other element of said machine.

Abstract: A force control throttle suitable for military or civil aircraft which is stowable in a console when not required for use. Fore and aft forces applied to the throttle handle by the pilot are sensed by pressure transducers which generate, in response, signals for controlling engine thrust. Tactile information relating to engine thrust demand is fed back to the pilot by means of a drive motor which tilts the throttle handle as fore or aft pressure is exerted. The angle of tilt is a function of the degree of pressure exerted and the demanded engine thrust.

Abstract: Control apparatus of the kind disclosed in UK patent specification Nos. 2,073,887 and 2,114,717, i.e. in which a movable operating member, arranged to control associated apparatus such as an aircraft engine, is coupled to an electric stepper motor, the motor being energizable to move the operating member and/or to generate a `feel` resistance to, or detents in, the manual movement of the operating member, the apparatus including a ball-screw assembly comprising a lead-screw and ball-nut, one of which is connected to the operating member and, with the operating member, is linearly movable with respect to the other, the stepper motor being coupled to the ball-screw assembly so that rotation of the motor rotor produces, or is produced by, relative rotation of the lead-screw and ball-nut.

Abstract: A simulator handgrip is connected to the shaft of a slip clutch which offers resistance to handgrip displacement, thereby simulating the "feel" of an actual thrust control for aircraft. Linkages are provided for measuring the amount of handgrip displacement as an electrical signal that may be utilized by a simulator computer. Adjustment devices are provided for moving the handgrip and clutch devices along a diagonal direction to accommodate pilots of different height.

Abstract: A control lever is provided for effecting positional control of a work implement. An actuator means applies a force to the control lever in response to a sensed load being applied to the work implement. The force applied to the implement control lever is in proportion to the load being applied to the work implement, thereby giving the operator a feel for the load being applied to the implement.

Abstract: A hand-held controller for a robot end effector having force and position control is disclosed. A single tactile area of the operator's hand, such as one finger, responds to two distinct feedback "feels" which are created by movement of a single element in two degrees of freedom that are both pivotable and rotatable in nature. Rotation of the trigger contacting element about its longitudinal axis is responsive to and reflects the amount of grasp force exerted by the end effector. Deflection of a guard encasing that trigger around a pivot point is responsive to and reflects the amount of movement of the end effector. The operator controls the position and grasp force of an end effector by exerting pressure against the trigger guard and, in turn, can "feel" two distinct feedbacks at the control finger. The feedback is indicative of both the grasp force and position of the controlled end effector.

Abstract: Spring-loaded linkage contained in a housing attached to the control stick of an aircraft. One member of the linkage is an arm having an end projecting from the housing and forming a hand grip through which the pilot controls the aircraft. The linkage provides a resisting force on the arm which prevents it from rotating relative to the control stick during normal flight maneuvers. However, when the control stick is pulled to full aft stop and additional pull equal to the spring break-out force is applied, the resisting force suddenly decreases, and the arm and grip rotate aft a discrete displacement relative to the control stick. This displacement actuates a g-limiter override which permits the aircraft to exceed set limits on its normal acceleration. The discrete displacement also provides the pilot with a tactile signal that the override has been actuated. The g-limiter override condition can be maintained by a pull on the grip substantially less than the spring break-out force.

Abstract: An aircraft controls simulator, for use with a computer programmed for aircraft flight simulation, having a yoke, a throttle control and a rudder control. A cabinet has a shaft extending therefrom attached to a simulated yoke control. The shaft operates an elevator potentiometer responsive to horizontal movement of the shaft and an aileron control responsive to rotation of the shaft. A throttle knob connected to a second shaft operates a throttle potentiometer. A foot operated potentiometer produces rudder control signals. A cable connects the potentiometers to the computer which utilizes the potentiometer positions to operate the flight simulation program.

Abstract: Pilot workload is reduced in a helicopter having a force-type, multi-axis sidearm control stick by providing a displacement-type control stick for collective blade pitch control. Either stick may be used by the pilot. When the force-type stick is employed, a trim system causes the displacement-stick to track a collective position command signal which is provided to the blade actuators. Changeover of control to the displacement-type control stick is accomplished either with a switch, or by moving the collective-type control stick. The signals associated with each control stick are alternately faded in and out to assure a smooth transition when collective control is switched over from one to the other.

Abstract: The steering or control force for operating a steering column in an aircraft, especially in a rotary wing aircraft, is stabilized. The steering column influences through an articulated steering or control linkage the elevator assembly or the rotor blade adjustment, whereby a signal is employed which is dependent on the measured flight speed. It is necessary to signal to the pilot at all times how the steering column must be moved. Such signalling must be definite and free of any disturbing influences and the pilot must receive such signalling through the steering column manual force which is a force reacting to the operation of the steering column. For this purpose a speed dependent signal is supplied to a servomotor. This signal rises with the flight speed at least above a preselectable threshold value. The servomotor in turn controls the tensioning state of a spring which is pivoted at one end to the steering column and at the other end to the displacement member of the servomotor.

Abstract: Computer-augmented electromechanical system is provided for controlling the tongs of a servomanipulator. The mechanical tongs are motor-driven through the remote slave arm of the manipulator, and the motor control current is supplied by a position sensor which senses the position of a spring-loaded trigger in the master arm handle on the manipulator. The actuator for the tongs provides the operator with artificial force reflection in a unilateral force-force control loop.

Abstract: Control force errors are automatically eliminated in aircraft, especially licopters. Such errors may occur because of disturbing forces that act on a control stick (1) for the elevator and/or rotor blade adjustment. The following features are combined. A main control drive (3) for the adjusting of the elevators and/or rotor blades is connected through a control linkage (2) with the control stick (1). A spring box (5) with a pretensioned spring (17) is connected through a control rod (14) to the control stick (2) and to one end of the spring box (5). A trimming rod (15) of a trimming motor (4) is operatively connected to the other end of the spring box (5). To compensate the disturbing forces caused by the inertial mass forces acting upon the control stick (1) as much as possible there are further provided two displacement pickups (6) and (7) or a single displacement difference forming pickup (16). A first summing circuit (8) receives the output signals from the two pickups (6, 7).

Abstract: Disclosed are apparatus and methods for simulating a control system such as an aircraft flight control system. Image generating and display apparatus for use in conjunction with the simulated control system are disclosed. Also disclosed are apparatus and a method for simulating a movable control such as an aircraft control wheel or rudder pedals for a system in which force and movement parameters of the control can be varied in accordance with simulated operation of the system. A lever having an adjustably positioned fulcrum is utilized in the simulation of the movable control. The application further discloses a flight simulator having a pilot's console and an instructor's console interconnected by a computer. The simulator enables the pilot to "fly" an aircraft while permitting the instructor and computer to introduce various different flight and aircraft conditions into the flight simulator.

Abstract: An all-electric powered flight control system for an aircraft incorporating fault-tolerant avionics combined with a redundant power actuation control system utilizing electro-mechanical devices for actuating aerodynamic control surfaces; and wherein, the redundancy is implemented through the division of the total aerodynamic surface area to be actuated into multi-segments, with each control segment having its own channel in the avionic control system. The avionic control system is effective in minimizing the effects of power actuated control loads reacting through aircraft structure by the incorporation of an electronic gain control power module which is positioned between the power output side of an actuator (e.g., an electro-mechanical or electro-hydraulic device) and the aerodynamic control surface or segment being actuated.

Abstract: A flight control surface (1) is supported from an aircraft frame structure (12), for pivotal movement about a hinge axis. The surface (10) is deployed against an aerodynamic load which is a function of surface deflection and imposes a torque on the flight control surface (10) wanting to rotate it back to a neutral trim position. A counterbalancing hydraulic actuator (16, 16', 226, 334, 372, 402) is connected between the frame structure (12) and the flight control surface (10). This actuator (16, 16', 226, 334, 372, 402) is oriented to oppose a counterbalancing torque on the flight control surface (10) acting in opposition to the torque imposed by the aerodynamic load. A controllable, separate actuator (34, 312, 422) is interconnected between the frame structure (12) and the flight control surface (10) and is operated for positioning the flight control surface (10).

Abstract: In a control system having a manipulatable unit, such as an aircraft stick, which is biased toward a neutral position to provide control "feel", an input which at each instant signifies the position of displacement of the stick from its neutral position is processed to provide an output signifying the magnitude of the biasing force to be applied to the stick. In a range of positions spaced to one side of its neutral position (or in such a range at each side of neutral) the output provides for a steep biasing force gradient as the stick is moved through a predetermined distance in either direction from a turning point to which the stick had been brought by movement in the opposite direction. For all other movements of the stick within that range the biasing force has a low gradient. The higher gradient of bias for small trimming movements provides better feel for trimming without requiring stick bias to be unduly stiff during coarser stick displacements.

Abstract: The torque gain of an electric motor assisted power steering system is modified as a function of the estimated level of road load friction such that the relationship between the operator exerted steering torque and the resulting rate of steer is substantially insensitive to a reduction in the level of road load. The road load is estimated as a function of the operator exerted steering torque, the torque assist provided by the electric motor, and the resulting steer rate.

Abstract: Control apparatus comprising a lever, foot pedal or other operating member which is coupled to an electrical stepper motor operable, under the control of a computer say, to generate detents and feel forces resisting the movement of the member and thereby impart information to the operator. For example, a detent or position of marked resistance can be introduced into the movement range of say a car throttle pedal to indicate to the driver a pedal position giving optimum economy of fuel. The detent position can be changed within the overall range of pedal movement in dependence upon instant driving parameters such as speed. As well as detents, programmed and/or external condition dependent feel forces can be generated.

Abstract: Control apparatus of the kind disclosed in our U.K. patent application No. 2173887 wherein the `mover` or rotor of a linear or rotary electrical stepper motor is coupled to a manual operating member so that, not only can the motor drive the operating member to give an automatic mode of the apparatus, but can exert a controlled resistance to manual movement of the operating member thereby giving a degree of `feel` to the operator and/or one or more electrically generated discreet detent positions within the range of movement. Herein the apparatus incorporates an improvement whereby the movable operating member is pivotably mounted so that the manual movement is arcuate--flexible cables connected to the drive motor mover and/or control switches incorporated in the operating member can pass from the operating member to a fixed part of the apparatus at or near the pivotable mounting where the movement to be taken up is less.

Abstract: An improvement to an aircraft control stick is disclosed. Movement of an aircraft may generate a force which undesirably causes the aircraft pilot to deflect the aircraft's control stick, which thereby results in the aircraft deviating from the desired flight path. The present invention includes a processor-based system which employs an algorithm that generates a signal for causing the control stick to resist such forces. The invention includes a spring and damper connected to the control stick so that the spring constant and damping ratio may be varied.