Patent Publication Number: US-10761557-B2

Title: Magnetic spring inceptor

Description:
CROSS REFERENCE TO OTHER APPLICATIONS 
     This application is a continuation of co-pending U.S. patent application Ser. No. 14/372,900 entitled MAGNETIC SPRING INCEPTOR filed Dec. 8, 2016 which is incorporated herein by reference for all purposes. 
    
    
     BACKGROUND OF THE INVENTION 
     Hand-operated controls, such as aircraft control sticks, joysticks, and other manual input devices operated at least in part by hand, collectively referred to herein as “inceptors”, enable a pilot or other operator to provide manual input to control a controlled system, such as an aircraft, a drone or other remote control aircraft, a guided weapon, an electronic game, a robot or robotic arm or other element, heavy equipment, etc. Depending on the design, an operator may provide input by one or more of manipulating a hand grip in one or more directions, such as side-to-side, forward-and-back, and/or twisting about a vertical axis; operating a trigger or other finger-operated input device; and manipulating a thumb-operated input device, such as a thumbwheel, thumb-operated joystick, or button. 
     In simple mechanical systems, such as older aircraft, a control stick or other inceptor may be linked mechanically to a corresponding control surface of the aircraft. In most modern aircraft, however, control stick inputs cause an electronic output representative of the manual input to be provided. A flight control system may use the electronic output to determine and send control signals to corresponding flight control surfaces and/or motors, referred to collectively herein as “actuators”. 
     In such electronic control systems, in aircraft and in other applications, a control stick may be equipped with mechanical springs or other structures configured and positioned so as to tend to return the control stick to a center position once the stick is released. In some systems, the springs may be configured to provide a haptic feedback to the operator (e.g., a sense of push back or resistance) so the operator has a sense that the desired input is being provided, including in some cases by giving the operator a sense of a degree to which the input device has been actuated within an available operating range. 
     Inceptor springs may be subjected to repeated stresses and as a result may fail after a certain number of cycles. Springs may exhibit a non-linear behavior at or near zero displacement, requiring pilots or other operators to apply a “breakout force” to manipulate an inceptor from the zero or “center” position, which some pilots may not find to be desirable. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Various embodiments of the invention are disclosed in the following detailed description and the accompanying drawings. 
         FIG. 1  is a diagram illustrating an embodiment of a multicopter aircraft. 
         FIG. 2  is a block diagram illustrating an embodiment of a flight control system. 
         FIG. 3  is a block diagram illustrating an embodiment of a magnetic spring inceptor. 
         FIG. 4A  is a diagram illustrating an embodiment of an x-y axis magnetic spring section of a magnetic spring inceptor. 
         FIG. 4B  is a diagram illustrating an embodiment of an x-y axis magnetic spring and sensor section of a magnetic spring inceptor. 
         FIG. 5  is a block diagram illustrating from a top down view an embodiment of a z axis magnetic spring section of a magnetic spring inceptor. 
         FIG. 6  is a flow chart illustrating an embodiment of a process to map magnetic spring inceptor sensor output to flight control commands. 
     
    
    
     DETAILED DESCRIPTION 
     The invention can be implemented in numerous ways, including as a process; an apparatus; a system; a composition of matter; a computer program product embodied on a computer readable storage medium; and/or a processor, such as a processor configured to execute instructions stored on and/or provided by a memory coupled to the processor. In this specification, these implementations, or any other form that the invention may take, may be referred to as techniques. In general, the order of the steps of disclosed processes may be altered within the scope of the invention. Unless stated otherwise, a component such as a processor or a memory described as being configured to perform a task may be implemented as a general component that is temporarily configured to perform the task at a given time or a specific component that is manufactured to perform the task. As used herein, the term ‘processor’ refers to one or more devices, circuits, and/or processing cores configured to process data, such as computer program instructions. 
     A detailed description of one or more embodiments of the invention is provided below along with accompanying figures that illustrate the principles of the invention. The invention is described in connection with such embodiments, but the invention is not limited to any embodiment. The scope of the invention is limited only by the claims and the invention encompasses numerous alternatives, modifications and equivalents. Numerous specific details are set forth in the following description in order to provide a thorough understanding of the invention. These details are provided for the purpose of example and the invention may be practiced according to the claims without some or all of these specific details. For the purpose of clarity, technical material that is known in the technical fields related to the invention has not been described in detail so that the invention is not unnecessarily obscured. 
     A magnetic spring inceptor is disclosed. In various embodiments, one or more magnetic springs may be used to return a control stick or other inceptor to a center or other neutral position and/or to provide haptic feedback (e.g., of resistance) to an operator. The magnetic spring(s) may include one or more stationary magnets that remains stationary relatively to the control stick; one or more non-stationary magnets coupled to a movable element of the control stick, in proximity to the stationary magnet and positioned opposite the stationary magnet in a position offset from the stationary magnet when in the neutral position, with like magnetic poles of the stationary and non-stationary magnets facing each other; and one or more sensors that detect changes in a magnetic field, such as may be produced when one or more of said non-stationary magnets is moved relative to one or more of said non-stationary magnets, such as when a hand-manipulated movable element of the inceptor is moved by an operator. 
     In some embodiments, a non-stationary magnet may be integrated with a hand grip portion of an inceptor assembly. The hand grip may be affixed to an upper portion of a split inceptor shaft, the upper and lower portions of which may be coupled by a universal joint, such as a Hooke joint, in a manner that allows the hand grip to be tilted fore-and-aft and side-to-side about a center of rotation that coincides with one or both of the universal joint and a geometric or other center of the hand grip. In some embodiments, the non-stationary magnet may be a large cylindrical ring affixed inside an inner cavity of the hand grip. The non-stationary magnet in some embodiments has a sufficiently large inner diameter to allow the lower portion of the inceptor shaft to extend through the center of the non-stationary magnet. A stationary magnet, in some embodiments a smaller cylindrical ring in shape, may be affixed to the lower portion of the inceptor shaft. The lower portion of the inceptor shaft in some embodiments is secured in and to a base assembly in a manner that prevents movement relative to an x-y plane of the inceptor while allowing the lower portion of the inceptor shaft to be rotated about a longitudinal axis of the lower portion of the inceptor shaft, e.g., an axis orthogonal to the x-y plane of the inceptor. 
     In various embodiments, manipulation of the hand grip relative to the x-y plane of the inceptor, such as by tilting the handgrip forward or back, or from side to side, causes at least a part of the non-stationary magnet to be moved nearer to a corresponding part of the stationary magnet, bringing like magnetic poles of the respective magnets into closer proximity and thereby producing a repulsive force at least a component of which acts in a direction opposite a direction in which the non-stationary magnet is caused to be moved by the manipulation of the hand grip by the operator. 
     In various embodiments, movement of the non-stationary magnet as described above results in a corresponding change in a magnetic field produce collectively by the non-stationary and stationary magnets. In some embodiments, one or more linear Hall sensors may be used to measure changes in at least a component of said magnetic field that is orthogonal to the x-y plane of the inceptor. The sensor provides an output that is proportional to the change in the magnetic field. The sensor output may be mapped to one or more associated input values, such as input values for one or both of pitch and roll in the context of aircraft control. 
     In some embodiments, a magnetic spring inceptor as disclosed herein may be used to provide a “yaw” or other input associated with rotation about a vertical or other axis orthogonal to an x-y or other reference plane of the inceptor. As in an example described above, at least a lower portion of an inceptor shaft may be mounted so as to be free to be rotated about its longitudinal axis, e.g., by twisting a hand grip about a central, substantially vertical axis. Magnetic spring resistance and/or return to neutral is provided in various embodiments by operation of a non-stationary set of magnets disposed radially around the inceptor shaft and affixed to a structure that is coupled to and rotates with the shaft, and a stationary set of magnets that remains stationary relative to a base assembly of the inceptor (i.e., does not move as the shaft rotates relative to the base), the stationary magnets being positioned opposite the non-stationary magnets in positions offset from the stationary magnets when in the neutral position, with like magnetic poles of the stationary and non-stationary magnets facing each other. Rotation of a hand grip or other manually (i.e., hand) operated movable structure of the inceptor rotates the non-stationary magnets to positions nearer corresponding ones of the stationary magnets, with like magnetic poles facing, producing a repulsive force at least a component of which acts in a direction opposite a direction in which the hand grip is being rotated by the operator. 
     In various embodiments, the inceptor includes one or more sensors that detect magnetic field changes produced when said non-stationary magnets are moved relative to said non-stationary magnets as described in the preceding paragraph, such as when a hand grip of the inceptor is rotated (twisted) about a substantially vertical axis by an operator. The sensor output in various embodiments may be mapped to a control value, such as a “yaw” or other control value. 
       FIG. 1  is a diagram illustrating an embodiment of a multicopter aircraft. In various embodiments, a magnetic spring inceptor as disclosed herein may be included in a multicopter aircraft as shown in  FIG. 1 . In the example shown, aircraft  100  includes a fuselage (body)  102  and wings  104 . A set of three underwing booms  106  is provided under each wing. Each boom  106  has two lift fans  108  mounted thereon, one forward of the wing and one aft. Each lift fan  108  may be driven by an associated drive mechanism, such as a dedicated electric motor. One or more batteries (not shown) and/or onboard power generators (e.g., small gas turbine) may be used to drive the lift fans  108  and/or charge/recharge onboard batteries. 
     In the example shown in  FIG. 1 , a propeller  110  is mounted on the fuselage  102  and configured to push the aircraft through the air in the forward (e.g., x axis) direction when in a forward flight mode. The propeller  110  is positioned between a pair of tail booms  112  that extend aft and are joined at their aft end by a tail structure on which aerodynamic control surfaces including elevators  116  and rudders  118  are mounted. In various embodiments, each of the inboard booms  106  forms at least in part an integral part of the corresponding port/starboard side tail boom  112 . In some embodiments, the tail booms  112  comprise extensions aft from the respective inboard booms  106 . For example, the tail booms  112  may be formed as part of or fastened (e.g., bolted) to an aft end of the corresponding inboard boom  106 . Additional control surfaces include ailerons  114  mounted on the trailing edge of wings  104 . 
     In various embodiments, lift fans  108  may be used to provide lift to enable the multicopter aircraft  100  to takeoff, hover, and/or land vertically (or within a short horizontal distance) in a vertical flight mode. The multicopter aircraft  100  may be configured to use lift fans  108  to take off vertically, for example, and then transition into a forward flight mode in which the aircraft is pushed through the air by propeller  110  and the wings  104  provide lift. In the forward flight mode, in various embodiments, a lift fan lock mechanism as disclosed herein is used to lock lift fans  108  in a locked position. 
     In various embodiments, a magnetic spring inceptor as disclosed herein may be incorporated into multicopter aircraft  100  and may be configured to be used to control flight. For example, a magnetic spring inceptor as disclosed herein may be used by a pilot or other operator of multicopter aircraft  100  to control attitude of the multicopter aircraft  100 , such as by indicating desired directions and/or degrees of pitch, roll, and/or yaw about corresponding axes with respect to a center of gravity (or other rotational center)  120 . Roll, pitch, and/or yaw inputs provide via a magnetic spring inceptor as disclosed herein may be used by an onboard flight controller (e.g., a flight computer comprising flight control software running on a general purpose or special purpose hardware processor) to control aircraft attitude and flight by providing corresponding control signal to all or a subset of actuators, such as lift fans  108  and aerodynamic control surfaces  114 ,  116 , and  118 . 
       FIG. 2  is a block diagram illustrating an embodiment of a flight control system. In various embodiments, flight control system  200  of  FIG. 2  may be included in and configured to control flight of an aircraft, such as multicopter aircraft  100  of  FIG. 1 . In the example shown, flight control system  200  includes a set of control stick (or other manual input device) sensors  202 , which provide a set of sensor outputs  204  representative of a position to which an associated control stick (or other manual input device or “inceptor”) has been manipulated. In various embodiments, sensors  202  may be included in a magnetic spring inceptor as disclosed herein, and sensor outputs  204  may be representative of detected changes in a magnetic field caused by manipulation of the magnetic spring inceptor in a manner that causes one or more magnets comprising the inceptor to be moved and/or reoriented, relative to one or more other magnets, a reference frame, etc. 
     In some embodiments, sensors  202  include one or more sets of Hall effect sensors. A Hall effect sensor is a transducer that varies its output voltage in response to a magnetic field. One type of Hall effect sensors is the “linear” Hall effect sensor, the voltage output of which varies linearly with magnetic flux density. In some embodiments, sensors  202  may include a set of linear Hall sensors configured to detect changes in a magnetic field orthogonal to an x-y plane of an inceptor. In some embodiments, sensors  202  may include two sets of linear Hall sensors, including a first set oriented to detect magnet field changes associated with side-to-side manipulation of an inceptor with which the sensors are associated and a second set oriented to detect magnet field changes associated with forward-and-back manipulation of the inceptor. 
     The flight control system  200  of  FIG. 2  includes a control input mapping module or block  206  configured to receive sensor outputs  204  and map such outputs  204  to corresponding roll, pitch, and/or yaw commands  208 . For example, control input mapping module or block  206  may be a software module running on a general purpose or special purpose processor, and may comprising computer instructions to perform table lookups based on outputs  204  (e.g., respective voltage levels provided as output by each of a plurality of Hall sensors) to determine for a given set of sensor outputs  204  a corresponding set of roll, pitch, and/or yaw commands, as applicable. 
     In the example shown in  FIG. 2 , the roll, pitch, and/or yaw commands  208  are provided as inputs to a conventional flight controller  210 , sometimes referred to as a flight control computer. The flight controller  210  may comprise software instructions executed by a processor, and may include computer instructions to determine for a given set of roll, pitch, and/or yaw commands  208  a corresponding set of control inputs  212  to be provided to corresponding aircraft “actuators”  214 , such as lift fans, propellers, and/or aerodynamic control surfaces such as rudders, elevators, and ailerons. 
       FIG. 3  is a block diagram illustrating an embodiment of a magnetic spring inceptor. In various embodiments, magnetic spring inceptor  300  of  FIG. 3  may be incorporated into an aircraft, such as multicopter aircraft  100  of  FIG. 1 , to provide manual control inputs to a flight control system, such as flight control system  200  of  FIG. 2 . 
     In the example shown, magnetic spring inceptor  300 , which is shown in  FIG. 3  in a front view (at left) and a left side view (at right), includes a hand grip  302  comprising a rigid casing surrounding an at least partly hollow core. A set of thumb operated controls  304  are mounted on a faceplate at a distal, free-moving end of the hand grip  302 . In the example shown, thumb operated controls  304  include a central thumbwheel and left/right buttons. In some embodiments, thumb operated controls  304  may be manipulated to generate electrical and/or electronic inputs to which electronics not shown in  FIG. 3  are responsive. Thumb operated controls  304  may be used to operate a cursor, control altitude, activate weapons or other auxiliary or non-flight control systems, etc. 
     As indicated by the axes and arrows shown at the top of  FIG. 3 , in various embodiments the magnetic spring inceptor  300  of  FIG. 3  may be used to control one or more of roll, pitch, and/or yaw of an aircraft. In the example shown, roll is controlled by manipulating hand grip  302  side-to-side, pitch is controlled by manipulating hand grip  302  side-to-side, and yaw is controlled by twisting hand grip  302  about a vertical axis, as shown. In the example shown, hand grip  302  is mounted rigidly to an upper axial shaft  306 . Upper axial shaft  306  in turn is couple via a universal joint  310 , such as a Hooke joint, to a lower axial shaft  308 . 
     A lower end of lower axial shaft  308  extends into a base assembly  312  of magnetic spring inceptor  300 , and is rotatably mounted in and to the base assembly  312  by a journal (or other) bearing or coupling  314  and an associated bearing nut  316 . Together, bearing/coupling  314  and bearing nut  316  secure lower axial shaft  308  in the upright position shown, preventing the lower axial shaft  308  from being moved vertically or laterally, while allowing lower axial shaft  308  to be rotated about its longitudinal axis, corresponding in this example to the yaw input/axis as shown. A flexible coupling  318 , e.g., a sleeve made of rubber or other flexible material, prevents dirt from entering an interior cavity of base assembly  312  while allowing hand grip  302  to be manipulated about three axes, i.e., side-to-side, fore-and-aft, and twisted about a longitudinal/vertical axis. Universal joint  310  transmits torsional (twisting) forces applied via hand grip  302  to the lower axial shaft  308 , enabling yaw inputs to be provided and detected as described more fully below. Universal joint  310  in various embodiments transmits torsional forces regardless of an angular position of the hand grip  302 , e.g., relative to a neutral or other reference position in an x-y plane of magnetic spring inceptor  300 , while allowing hand grip  302  to be manipulated side-to-side and/or forward-and-aft, for example by rotating hand grip  302  right or left and/or forward or back about a center of rotation that coincides with universal joint  310 . 
     Referring further to  FIG. 3 , in the example shown non-stationary magnet(s)  320  is/are mounted within hand grip  302  in a position adjacent to a stationary magnet  322  mounted fixedly on lower axial shaft  308 . In various embodiments, non-stationary magnet  320  may be a single magnet, for example a magnet shaped as a ring. Stationary magnet  322  may be a smaller ring coupled fixedly to lower axial shaft  308 . In various embodiments, the non-stationary magnet  320  and stationary magnet  322  each may be polarized substantially along a longitudinal axis, resulting in magnets having opposite poles on the upper and lower faces of the magnets  320 ,  322 . In various embodiments, the non-stationary and stationary magnets  320 ,  322 , respectively, may be incorporated into a magnetic spring inceptor as disclosed herein, such as magnetic spring inceptor  300  of  FIG. 3 , with like poles facing each other, resulting in a repulsive force being generated and experienced when the hand grip (e.g., hand grip  302 ) is manipulated relative to a neutral position (e.g., a position substantially orthogonal to an x-y plane of the magnetic spring inceptor  300 ). In the example shown in  FIG. 3 , for example, tilting the hand grip  302  side-to-side and/or fore-and-aft would cause the hand grip  302  to be rotated about a center of rotation coincident or otherwise associated with the universal joint  310 , resulting in at least a portion of the non-stationary magnet(s)  320  to be moved nearer to non-stationary magnet  322 . Since the faces/sides of non-stationary magnet(s)  320  and stationary magnet  322  having the same polarity would be brought near to each other, a repulsive magnetic force would be generated and experienced by the operator, providing haptic feedback similar to that provided in conventional inceptors by mechanical springs. In some embodiments, the magnetic repulsive force may tend to return the hand grip  302  to the neutral position, e.g., if the operator were to release the hand grip  302  and/or release at least some of the force applied to manipulate the hand grip  302 , similarly to the way in which in conventional inceptors mechanical springs may be used to return a hand grip to a neutral/center position. 
     In various embodiments, changes in the net magnetic field generated by changing the position of the non-stationary magnet(s)  320  relatively to the stationary magnet  322  may be measured to determine a roll and/or pitch command/level associated with manipulation of the hand grip  302 . Referring further to  FIG. 3 , the magnetic spring inceptor  300  further includes a set of upper sensors  324 . In some embodiments, the upper sensors  324  may include a plurality of linear Hall sensors disposed on a substrate. The linear Hall sensors may be deployed on either side of the magnets  320 ,  322 , for example along axis with respect to which inputs provided via magnetic spring inceptor  300  is to be used to be sensed, such as the x (e.g., roll) and y (e.g., pitch) axes of magnetic spring inceptor  300 . 
     In some embodiments, manipulation of hand grip  302  relative to the x and/or y axes of magnetic spring inceptor  300  may be sensed and measured by comparing the output of linear Hall sensors comprising related pairs (or larger sets), each pair (or larger set) associated with a corresponding detection axis. For example, in the case of a pair of x-axis (roll) sensors having outputs H 2  and H 1 , respectively, a normalized distance (difference) may be computed as follows: 
                 H   2     -     H   1           H   2     +     H   1             
The resulting normalized difference value may be used to perform a lookup to determine an associated roll (or pitch) command level to which the operator input provided via manipulation of the magnetic spring inceptor is mapped. In some embodiments, such mapping is performed by a control input mapping module, such as control input mapping module  206  of  FIG. 2 .
 
     In various embodiments, one or more of the size, shape, and strength of the non-stationary magnet(s)  320  and stationary magnet  322 , along with the orientation, placement, and relative spacing in the horizontal and vertical directions (as shown in  FIG. 3 ) are selected at least in part to achieve a desired level of magnetic repulsive force as the non-stationary magnet(s)  320  is/are brought into closer proximity to stationary magnet  322  due to manipulation of hand grip  302 , as described above. The desired force may be determined by a design engineer based at least in part on considerations such as achieving a force necessary to return the hand grip  302  to the neutral position, e.g., upon force being applied by an operator to the hand grip being released, and/or a desired level of haptic feedback to the operator. 
     In various embodiments, one or more of the size, shape, and strength of the non-stationary magnet(s)  320  and stationary magnet  322 , along with the orientation, placement, and relative spacing in the horizontal and vertical directions (as shown in  FIG. 3 ), and in addition the characteristics and arrangement of the upper sensors  324 , and the placement of sensors  324  relative to the magnets  320 ,  322 , in both the horizontal and vertical directions, are selected at least in part to achieve a desired range of sensor output (response) through an expected range of motion of the non-stationary magnets  320  relative to one or both of the sensors  324  and stationary magnet  322 . 
     Referring further to  FIG. 3 , in the example shown magnetic spring inceptor  300  includes components to provide magnetic spring resistance to manipulation of hand grip  302  about a substantially longitudinal/vertical (e.g., z or yaw) axis of magnetic spring inceptor  300 . Specifically, in the example shown, magnetic spring inceptor  300  includes a set of non-stationary magnets  326  coupled mechanically to lower axial shaft  308  by a mounting plate  328  fixedly attached to lower axial shaft  308 . As the lower axial shaft  308  is rotated about its longitudinal axis, e.g., in response to a twisting force/torque applied to/via hand grip  302 , the mounting plate  328  and non-stationary magnets  326  rotate with it (i.e., with lower axial shaft  308 ). A complementary set of stationary magnets  330  are disposed on a base  332  mounted fixedly within base assembly  312 , such that the stationary magnets  330  do not move when the lower axial shaft  308 , and the non-stationary magnets  326  coupled thereto, are rotated. 
     In various embodiments, non-stationary magnets  326  and stationary magnets  330  are mounted with like magnetic poles facing each other (e.g., north pole facing down in the case of non-stationary magnets  326  and up in the case of stationary magnets  330 ). As a result, as lower axial shaft  308  is rotated about its longitudinal axis, non-stationary magnets  326  come into closer proximity to adjacent ones of stationary magnets  330 , resulting in a magnetic repulsive force being generated and experienced. Similar to the force described above with respect to the roll (x) and pitch (y) axes, the repulsive force in various embodiments tends to return the hand grip  302  to a neutral/zero position, e.g., once a twisting force/torque applied to the hand grip  302  by an operator is released. In addition, the strength, size, and arrangement of the non-stationary magnets  326  and stationary magnets  330  in various embodiments is such that a desired degree of haptic feedback is provided to the operator in response to the hand grip  302  being rotated about the longitudinal axis of lower axial shaft  308 . 
     Referring further to  FIG. 3 , magnetic force inceptor  300  further includes a set of lower (daughter) sensors  334  to detect/measure magnetic field changes associated with movement of non-stationary magnets  326  relative to stationary magnets  330  associated with rotation of hand grip  302  about the longitudinal axis of lower axial shaft  308 . In various embodiments, lower sensors  334  may be linear or other Hall sensors. Changes in sensor output may be normalized, as described above, and mapped to corresponding yaw command levels, similar to the processing described above with respect to the roll and pitch axes. Such processing may be performed in some embodiments by a control input mapping module, such as control input mapping module  206  of  FIG. 2 . 
     In various embodiments, the number and arrangement of one or both of non-stationary magnets  326  and stationary magnets  330  may be determined at least in part to minimize the effect that such magnets and/or movement thereof will have on the upper sensors  324 . For example, in some embodiments, an even number of non-stationary magnets  326  and stationary magnets  330  are used, and each set is arranged in a pattern that is symmetrical with respect to the x and y axes of magnetic force inceptor  300 . As a result, the non-stationary magnets  326  and stationary magnets  330  have no effect and/or offsetting effects with respect to the magnetic field component(s) measured by the upper sensors  324 , which in various embodiments may be configured to detect changes in a magnetic field component that is orthogonal to the x-y plane of magnetic spring inceptor  300 . 
       FIG. 4A  is a diagram illustrating an embodiment of an x-y axis magnetic spring section of a magnetic spring inceptor. In various embodiments, the structures shown in  FIG. 4A  may be used to implement correspondingly numbered structures in the magnetic spring inceptor  300  of  FIG. 3 . In the example shown, non-stationary magnet  320  comprises a single, ring-shaped magnet, having in this example the form of a relatively flat (i.e., height less than inner and outer diameter) right circular hollow cylinder. The upward pointing arrows indicate the non-stationary magnet  320  have been polarized in the direction of its longitudinal axis, with the “north” pole being associated with the upper face as shown, and the “south” pole being associated with the lower face (not visible in the view shown). Stationary magnet  322  coupled to lower axial shaft  308  is shown to comprise a smaller ring-shaped magnet, having a form similar to that of non-stationary magnet  320 . As shown, stationary magnet  322  has been magnetized along its longitudinal axis and has been oriented with its south pole facing up, as shown. As a result, the south pole face of non-stationary magnet  320  is opposite the south pole face of stationary magnet  322 . Movement of non-stationary magnet  320  relative to stationary magnet  322 , e.g., by manipulation of hand grip  302  as indicated by the left and right arrows shown originating at hand grip  302 , would result in a portion of non-stationary magnet  320  being moved nearer to an opposite portion of stationary magnet  322 , with like magnet poles facing, resulting in a magnetic repulsive force, as described above. 
       FIG. 4B  is a diagram illustrating an embodiment of an x-y axis magnetic spring and sensor section of a magnetic spring inceptor. In various embodiments, the structures shown in  FIG. 4B  may be used to implement correspondingly numbered structures in the magnetic spring inceptor  300  of  FIG. 3 . In some embodiments, the view shown in  FIG. 4B  may comprise in part a front cross-sectional view of the structures shown in  FIG. 4A . In the example shown in  FIG. 4B , left and right side parts of non-stationary magnet  320 , labeled as  320   a  and  320   b , respectively, in  FIG. 4B  are positioned opposite corresponding parts of stationary magnet  322 , labeled as  322   a  and  322   b , respectively, in  FIG. 4B , with like magnetic poles facing, as shown.  FIG. 4B  further shows linear Hall sensors  324  positioned below and outside the non-stationary magnet  320  and stationary magnet  322 . For clarity, the respective magnetic field of each magnet/portion thereof ( 320   a ,  320   b ,  322   a ,  322   b ) is represented by a single field line.  FIG. 4B  illustrates that in the neutral position, as shown, the magnet repulsive force between non-stationary magnet  320  and stationary magnet  322  would be minimal and in any case evenly balanced. Movement of the non-stationary magnet  320  left or right, as indicated by the curved black arrows would result in a magnetic repulsive force being generated due to the part of the non-stationary magnet  320  opposite the direction of movement being moved nearer a corresponding part of stationary magnet  322 . In addition, the movement would result in a change to the component of the net/combined magnetic that is orthogonal to the x-y plane (i.e., the vertical component as shown), which would be reflected in a measurable difference in the output of sensors  324 , the changed output of which can be mapped as described above to corresponding roll and/or pitch command levels. 
     In various embodiments, release of force on the hand grip  302  would result in the magnetic force inceptor returning to the neutral position, as shown, and the sensors providing equal output values, which in various embodiments would be mapped to a zero roll input and zero pitch input state. 
       FIG. 5  is a block diagram illustrating from a top down view an embodiment of a z axis magnetic spring section of a magnetic spring inceptor. In various embodiments, the structures shown in  FIG. 5  may be used to implement correspondingly numbered structures in the magnetic spring inceptor  300  of  FIG. 3 . In the example shown, mounting plate  328  is shown to have six evenly-spaced non-stationary magnets  326  mounted thereon, in an arrangement around lower axial shaft  308  that is symmetrical with respect to the pitch (horizontal, as shown) and roll (vertical, as shown) axes of the magnetic spring inceptor. A complementary, evenly offset array of stationary magnets  330  are shown to be disposed on base  332 . The non-stationary magnets  326  are oriented so as to have facing downward a pole of like polarity to an opposite side/face of stationary magnets  330 . 
     The upper image in  FIG. 5  shows the illustrated components in the neutral position. The lower image of  FIG. 5  shows the same components in a position in which the lower axial shaft  308  and the mounting plate  328  and non-stationary magnets  326  attached thereto have been rotated clockwise, to a position in which the non-stationary magnets  326  overlap with corresponding ones of the stationary magnets  330  positioned opposite them. As a result, a magnetic repulsive force would be present and would tend to push the non-stationary magnets  326 , and the mounting plate  328  and lower axial shaft  308  to which they are attached, back to the neutral position, as described above. 
     In various embodiments, rotating the components shown in  FIG. 5  to the position shown in the lower image of  FIG. 5  would result in changes to a combined magnetic field associated with the non-stationary magnets  326  and stationary magnet  330 , which would be measured by sensors such as lower sensors  334  of  FIG. 3 , the output of which may be mapped to a corresponding yaw (or other) input command, as described above. 
     As noted above, arranging the non-stationary magnets  326  and stationary magnets  330  in symmetrical patterns comprising even numbers of magnets results in those magnets having neutral/offsetting effects on the sensors associated with detecting pitch and/or roll inputs, as described above. 
       FIG. 6  is a flow chart illustrating an embodiment of a process to map magnetic spring inceptor sensor output to flight control commands. In various embodiments, the process of  FIG. 6  may be implemented by a component of a flight control system, such as control input mapping module  206  of  FIG. 2 . In the example shown, inceptor sensor output is received ( 602 ). For example, the output of one or more sets of Hall sensors, such as sensors  324  and/or  334  in the example shown in  FIG. 3 , may be received. Received sensors outputs (e.g., Hall sensor output voltages) are mapped to one or more of roll, pitch, and/or yaw commands/levels, as applicable ( 604 ). In various embodiments, sensor outputs associated with each of a plurality of axes (e.g., roll, pitch, and/or yaw, in the case of an aircraft) are received and mapped to a corresponding command/level for that axis. Roll, pitch, and/or yaw values to which received sensor outputs have been mapped, as applicable, are provided, e.g., to a flight controller such as flight controller  210  of  FIG. 2 . As new/changed inputs are received ( 608 ), the values are mapped to corresponding roll, pitch, and/or yaw values, as applicable ( 602 ,  604 ,  606 ). Processing of sensor output continues until done ( 610 ), e.g., the system being controlled by the magnetic spring inceptor is shut down. 
     In various embodiments, techniques disclosed herein may be used to provide an inceptor that returns to a center/neutral position and/or provides a haptic feedback (resistance) to an operator without using mechanical springs, which may wear out due to material fatigue after a certain number of cycles, and which may require that a “breakout” force be applied to begin to move them from a neutral position. In various embodiments, techniques disclosed herein may be used to sense magnetic field changes associated with manipulation of an inceptor, and to map associated sensor output values to corresponding control input values (e.g., commands) associated with corresponding axes, such as roll, pitch, and/or yaw commands, in the case of an inceptor used in flight control. 
     While one or more examples described above involve use of a magnetic spring inceptor as disclosed herein to control flight of an aircraft, a magnetic spring inceptor as disclosed herein may be used in other applications and contexts as well, including without limitation to control a cursor, a robot, electronic game play, a drone, a manned or unmanned spacecraft, an active or passive guided weapon (such as a guided missile or a bomb with remotely controlled aerodynamic control surfaces), a manned or unmanned watercraft, such as a submarine, a crane, a land based vehicle, heavy or light equipment, etc. 
     In various embodiments, a magnetic spring inceptor as disclosed herein may be used to provide return-to-center and/or to provide haptic feedback to an operator while using a sensor other than (or in addition to, or as a backup to) a Hall sensor or other magnetic field sensor to measure a degree of manipulation of the inceptor. For example, optical or other sensors may be used in some embodiments to sense a position of the magnetic spring inceptor relative to some reference. 
     While in a number of embodiments described above a magnetic force inceptor that can be rotated with respect to three axes (roll, pitch, and yaw, for example), is disclosed, in various embodiments, magnetic force inceptors embodying techniques disclosed herein may have more or fewer degrees of freedom. For example, in some embodiments, a magnetic spring inceptor as disclosed herein may comprise a joystick capable of being manipulated with respect to just the x and y axes (e.g., not a vertical or other longitudinal axis). Magnetic springs comprising non-stationary magnets disposed opposite and adjacent to corresponding stationary magnets, with like poles facing, may be used to provide a repulsive force as described herein to tend to return the joystick to a neutral position and/or to provide haptic feedback. For example, structures similar to non-stationary magnet  320  and stationary magnet  322  of  FIGS. 3, 4A, and 4B  may be used. In some embodiments, position of the joystick may be sensed using linear Hall sensors, similar to sensors  324  of  FIGS. 3 and 4B , and sensor outputs may be mapped to corresponding input/command levels. 
     In some embodiments, a twistable knob, wheel, or other manual input structure may comprise a magnetic force inceptor as disclosed herein. Structures similar to non-stationary magnets  326 , stationary magnets  330 , and lower sensors  334  of  FIGS. 3 and 5  may be used to provide a magnetic repulsive force that tends to return the manual input device to a center/neutral position and/or provide haptic feedback, to sense a degree to which the manual input device has been displaced, and to map the sensed displacement to a corresponding value or level of an associated input parameter. 
     In various embodiments, a magnetic force inceptor comprising manual input structures capable of being manipulated in one or more associated directions and/or about one or more associated axes may be provided, including without limitation a lever, thumbwheel, push button, or other manual input structures. 
     Although the foregoing embodiments have been described in some detail for purposes of clarity of understanding, the invention is not limited to the details provided. There are many alternative ways of implementing the invention. The disclosed embodiments are illustrative and not restrictive.