Extended motion control using electromagnetic forces

Abstract

This invention extends the prior art in EMECS to make force / torque responsive to externally imposed force / torque, in the same mechanism configuration. This is done by creating a hidden internal configuration parameter or parameters, which changes depending on the external force / torque imposed by the load. The hidden configuration enables automatic feedback in the system. The same facility is used to initialize the EMEC to deliver nominal force / torque.

Description

[0001] FORM 2 THE PATENT ACT 1970 (39 of 1970) & The Patents Rules, 2003 COMPLETE SPECIFICATION (See section 10 and rule 13)TITLE OF THE INVENTION: Extended Motion Control Using Electromagnetic ForcesAPPLICANT(S) I.NAME : GORUR NARAYANA SRINIVASA PRASANNA NATIONALITY : AN INDIAN CITIZEN ADDRESS : C / O IIIT-B, 26 / C, HOSUR ROAD, ELECTRONICS CITY, BANGALORE- 560100, KARNATAKA STATE, INDIA II.NAME : SMITHA SRINIDHI NATIONALITY : AN INDIAN CITIZEN ADDRESS : C / O IIIT-B, 26 / C, HOSUR ROAD, ELECTRONICS CITY, BANGALORE- 560100, KARNATAKA STATE, INDIA II.NAME : SHIVANI NATIONALITY : AN INDIAN CITIZEN ADDRESS : C / O IIIT-B, 26 / C, HOSUR ROAD, ELECTRONICS CITY, BANGALORE- 560100, KARNATAKA STATE, INDIA THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED. Contents Contents ..................................................................................................................................................2 1. FIELD OF THE INVENTION ............................................................................................................3 2. BACKGROUND .............................................................................................................................3 3. DISCUSSION OF PRIOR ART .........................................................................................................3 4. ABSTRACT AND SUMMARY .........................................................................................................4 Extended EMECS .............................................................................................................................4 Magnetic Circuit Designs .................................................................................................................4 Magnet Geometry ...........................................................................................................................5 Minimization of leakage flux ...........................................................................................................5 5. BRIEF DESCRIPTION OF DRAWINGS ............................................................................................6 6. DETAILED DESCRIPTION OF THE INVENTION ..............................................................................6 Sensing and Actuation Emecs .........................................................................................................6 7. BASIC MODULATING BLOCKS of EEMECS ....................................................................................8 7.1. EEMEC Initialization ....................................................................................................................8 8. FEEDBACK SYSTEM ......................................................................................................................9 Sensor and Actuator ..........................................................................................................................10 8.1. Feedback Dynamics ...................................................................................................................11 8.2. Correction of Phase Error ..........................................................................................................11 9. EXTENDED EPAIRS: Sensors and Actuators ...............................................................................12 9.1. EEPAIRS as Sensors ....................................................................................................................12 9.1.1. Prismatic Epair ..................................................................................................................14 9.1.2. Revolute Epairs ..................................................................................................................14 9.1.3. Screw Epair ........................................................................................................................14 9.1.4. Spherical Epair ...................................................................................................................14 9.1.5. Cylindrical Epair .................................................................................................................14 9.1.6. Type B Emec ......................................................................................................................14 9.2. EEPairs as Actuators ..................................................................................................................14 10. Modulation of Induction Force ..................................................................................................15 10.1. Extended Prismatic Pair ....................................................................................................15 10.2. Error Signal ........................................................................................................................18 11. Modulation of Flux Path Reluctance .........................................................................................19 11.1. Extended Revolute Pair .....................................................................................................19 11.2. Configurational Hysteresis Effects ....................................................................................20 12. Modulation of Magnetic Field Strength ....................................................................................21 12.1. Extended Revolute Pairs ....................................................................................................21 13. Other Pairs ................................................................................................................................21 14. Internal Hidden and External Observable Parameters .............................................................21 15. Composition of Extended epairs to yield extended emecs (EEMECs)........................................22 16. Apparatus using the invention ..................................................................................................23 CLAIMS ..................................................................................................................................................24 ABSTRACT ..............................................................................................................................................25 BACKUP MATERIAL NOT PART OF APPLICATION ..................................................................................26 1. FIELD OF THE INVENTION This is in the domain of motion control, and extends the ideas in US patent 7,348,754 and related Indian and US divisional patents. All the aspects of US patent 7,348,754 and related divisionals, and related applications in India (3083 / CHE / 2009, also as WO2011074000 and US 20130006589 A1) are extended. Specifically, all the apparatus mentioned therein can be extended in functionality as per the invention. All the content of these patents and patent applications – specification, drawings, claims, are incorporated herewith by reference, and referred to be the labelling in the respective documents. A companion publication (magnetic_flywheel_paper_accepted_changes_new.pdf) contains more disclosure material, and is separately attached, and the information there may be added to this patent application. As mentioned in these documents, EEMECS can be used in conjunction with or without manual or automatic control using microprocessors (e.g. Ganaka as per our prior patent applications), with or without electromagnets. We use the words Enhanced EMEC abbreviated as EEMEC to refer to this invention. 2. BACKGROUND Emecs are generalizations of motors to non-symmetrical geometries, and here we extend them to make them produce force / torque depending on externally imposed forces and / or torques, without a change in the externally visible configuration. Neither the changed force or torque in a given configuration, nor the distinction between external and internal configurations has been described in the prior art, and this is the subject of this invention. In addition, the ill-conditioning of asymmetric fields, and associated dynamics, has not been addressed in the prior art. 3. DISCUSSION OF PRIOR ART The prior art in motion control including the methods described in US patent 7,348,754, and corresponding Indian Patents, and divisionals, generalizes motors to non-cylindrical and non-linear geometries, and converts them to powered mechanisms. Magnetization of the pairs is described in US patent 7,348,754, but the geometric structure, dimensions, design and layout in space of the magnets and magnetic elements is not described, other than mentioning that the design has to be appropriate (other than the cutouts for induction members). Neither is the strength of the required magnets described. Nor are algorithms for making this design described. A few algorithms are described in US patent application 20130006589 and associated Indian Patent Applications. The prior art does not have a mechanism responding with a variable force / torque in the same position of the mechanism – the force / torque is statically determined by the detailed mechanism geometry (and mechanism velocity, if induction members are used). At a given mechanism configuration, the force / torque is fixed, and does not change with external force / torque imposed by the load. This can limit the application of passive emecs to deal with varying forces / torques / speeds of external loads / environments. It also introduces complications in initialization of the EMEC, as the structure is unchangeable with manufacturing errors, and system drift. This invention extends all the prior art, and can be used in conjunction with them. Only a few embodiments will be described here, but the claims extend to all the apparatus specified in the aforesaid prior art. Specifically, power control, power transmission control, and load control as per US 738554 can all the improved using this invention. A large number of apparatus are described in the said patent (including those in Section G), and this invention can improve them and / or utilize them as subsystems or otherwise. 4. ABSTRACT AND SUMMARY Extended EMECS This invention extends the prior art to make force / torque responsive to changes externally imposed force / torque, in the same externally observable mechanism configuration. This is done by creating a hidden internal configuration parameter or parameters, which changes depending on the external force / torque imposed by the load. These observable and hidden parameters are initialized to yield a nominal force / torque, and then allowed to change within limits as the external force / torque at one or more end effectors varies. These parameters can be set by the mechanism itself without active electronic control or set by electronic control using actuators, or by manual control. An EEMEC has observable external parameters like force, torque, position, angular position, etc, and internal hidden parameters (e.g. the inter magnetic separation / position). The hidden parameters change exemplarily statically w.r.t external force, leading to other parts of the mechanism, dependent on these hidden parameters, to change their behaviour w.r.t external force / torque. In addition to the above, the invention further extends the prior art as follows: Magnetic Circuit Designs The prior art does not describe how the required fields are to be produced by appropriate arrangement of magnets, and induction and hysteresis members, of suitable geometry (shape), dimensions., and location throughout the mechanism. Essentially there is no description of how the magnetic circuit is to be designed and implemented. Only the components to be used are mentioned – magnets, induction and hysteresis members. Magnet Geometry The magnetics is not uniquely specified by the desired dynamics – it is an under determined system, as in principle the magnetic moments of every point in space can be chosen to obtain the desired dynamics. The geometry, size and location at pairs (joints), and links, can be chosen to simplify manufacture, and to eliminate field artifacts caused exemplarily by discontinuities at boundaries. The elimination or reduction of these artifacts prevents them from causing undesirable spatial harmonics in the dynamics to appear and distort the dynamics. The geometric structure of the magnets, hysteresis and induction members, and their placement, to produce the resultant spatially varying fields is described in this invention. Minimization of leakage flux Finally, the design of the circuits to produce spatially varying fields, without leakage of magnetic flux to undesirable locations, is yet another aspect of this invention.

[0002] 5. BRIEF DESCRIPTION OF DRAWINGS Figure 1 EMEC control loop with sensor emec M1 and Actator / End Effector emec M2.......................7 Figure 2 Emecs Forming Control Loop ....................................................................................................7 Figure 3 Showing Multiple Sensors and Amplifiers ................................................................................7 Figure 4 Enhanced Magnetic Element Configurable in Position, orientation, and field distribution .....9 Figure 5 IC Engine EEMEC (Magnetic Flywheel) showing Angular Adjustment of Stator magnet position .................................................................................................................................................12 Figure 6 Array of magnets used as customizable sensor, with inverse quadratic and inverse forth power separation as a function of force ...............................................................................................13 Figure 7 Emec Sensor for force / Torque ................................................................................................14 Figure 8 Two Prismatic Pairs sharing the same guide, and interacting magnetically - force sensor ....15 Figure 9 Use of EMEC prismatic pair as forces sensor ..........................................................................17 Figure 10 Generation of Error Signal from External Force ....................................................................18 Figure 11 Flux Path of Revolute Pair EEMEC .........................................................................................19 Figure 12 Showing Multiple Combinations of Theta1 and Theta2 giving the same torque. Theta1 is the separation between two angular flux return path sectors (not shown). Theta2 is the angle between the rotor and stator magnets................................................................................................21 Figure 13 Extemded Emec in General ...................................................................................................22 Figure 14 Exemplary General Structure of an EEMEC ..........................................................................22 6. DETAILED DESCRIPTION OF THE INVENTION The key idea is illustrated in an embodiment as follows. Sensing and Actuation Emecs In the terminology of US 7,348,754, and the corresponding Indian patent, two emecs M1 and M2 are used (see Figure 1), with the first one M1, exemplarily controlling a structural member, active winding, or other elements of the second one, M2. The first emec M1 is a sensor / controller, and responds in a static manner to the load, and the 2ndemec M2, which is actuator (it can be static itself), responds in a variable manner to the load, depending on the configuration of the structural member set by the first emec. Effectively M2 amplifies the control signal produced by M1. Clearly this is a control loop, as redrawn in Figure 2. In certain embodiments, global interactions, exemplarily interaction between elements of different epairs manifests itself, and is used for both sensing and actuation. The aforesaid pairs form a cluster – a structure not present in the prior art.

[0003] The invention directly extends to cases where there is a cascade of sensors (emecs) and amplifiers, possibly connected in a network e.g. a series-parallel connection, as shown in Figure 3. The sensors and amplifiers may be emecs, or electronics circuits, or other systems, as per the existing state-of-art (Figure 3). In essence, we have a cluster of emecs working together to handle the load. The description below elucidates these further, by discussing how epairs can be extended, and assembled together to form complete EEMECS. 7. BASIC MODULATING BLOCKS of EEMECS The embodiments described in this Section are building blocks of EEMECS giving forces / torque responding to external forces / torques. Specifically, in Section 10, 11. And 12, we illustrate how the following changes in developed force / torque can be devised, at the same externally visible emec configuration, exemplarily without the use of electromagnets and / or electronic control. • An induction force / torque can change at the same relative linear / angular velocity between a magnetic member and an induction member. • Flux Path Reluctance leading to changes in field and force / torque, can be changed based on external force / torque • Magnetic Field Strength, leading to changes in field and force / torque, can be changed based on external force / torque These changes are determined by the sensor / controller emec, which converts the externally imposed force / torque to a change in its (hidden) configuration (exemplarily position), which in turn modulates the force / torque developed by the (visible) mechanism (the system). The same facility is used for EEMEC initialization, as described further below. 7.1. EEMEC Initialization The emec parameters – observable or hidden (position and orientation of magnets and induction / hysteresis members) have to be initialized, to generate the nominal force / torque profile. This initialization may be done statically, at the time of manufacture, or dynamically during operation, to compensate for system force / torque drift from the nominal value over time. The asymmetric and spatially varying fields and resulting force / torque profiles varying with emec configuration, cause addition or subtraction of magnetic fields and forces / torques produced by different magnetic elements - magnets, induction and hysteresis members - throughout the configuration space of the mechanism. The resulting field and force / torque distribution can be ill conditioned with respect to the location, shape, dimensions, and material properties of the magnetics, requiring active positioning and field control using auxiliary means (e.g. electromagnets). Phase mismatches (exemplarily in erroneous spatial positions) can lead to large errors in the force / torque profile generated by emecs. As per the paper draft attached, a 5 degree mismatch error in a magnetic flywheel for an IC engine, can increase torque ripple by 3-5 dB, necessitating partially active control. Initialization robust to manufacturing errors and system drift, magnified by ill conditioning, is an important element in emecs, and is not in the prior art. In an embodiment, this is achieved by setting the position and orientation of the magnetic elements (magnets, hysteresis and induction members), using active control (exemplarily electromagnets). The same active control provides an auxiliary magnetic field which is set to compensate for emec field setting errors. Such a magnet (and hysteresis and induction members) is installed on a powered actuator which can move linearly or angularly to synthesize the desired field / force / torque profile accurately. This actuator does not in general need an emec, and can even be manual. If the actuator is powered by an electromagnet, the same electromagnet can be exemplarily used to compensate for emec field setting errors. All these magnetic elements are initialized using exemplarily a gradient descent algorithm. In Figure 4, magnet M1 (with North pole N and South Pole S) used in the prior art (e.g. ubiquitously in US 7,348,754) is enhanced in this invention to a cluster of magnetic elements – M2 substantially the same as M1, and M3 and M4 (which may be the same as M3), which are used to change the position and orientation (3-D position and 3-D orientation) using magnet M3 as a positioner (exemplarily a coil driving a screw), and M4 generating auxiliary fields to accurately synthesized the required field and force / torque distribution. This diagram is exemplary, and the geometry and design of this cluster can differ from the illustration. An enhanced EMEC is composed of many such clusters (some of which may not have the position / field adjustable elements). The set of clusters is initialized such that the desired force / torque distribution is generated by the EEMEC. This is not present in the prior art for emecs. 8. FEEDBACK SYSTEM Feedback is built into the system. In other words, the magnetics (including induction and hysteresis members, flux return paths, air gaps, and magnets), change their relative position (part of which may not be externally observable), to change the externally observable force / torque developed by the mechanism. Every feedback system has an output sensor, a controller and an actuator (the system). All these can be exemplarily built using emecs. The extensive configurability of emecs enables a wide variety of sensors, controllers, and actuators with customizable input-output behaviour to be designed – exemplarily • Linear, with or without saturation • quadratic • general nonlinear. In the prior art, the use of emecs as sensors with configurable input-output functions, is not described. In an embodiment • The sensor detects the error - the difference between the target force / torque at the end effector, and the achieved target force / torque at the end effector. o The error may be filtered (low pass in an embodiment) • The error is used by the controller to change the mechanisms internal structure, so as to achieve the desired force / target torque. • The error from a nominal design force / torque is used to initialize the emec structure to deliver the nominal force / torque at the end effector. This overcomes deleterious effects of ill- conditioning due to spatially varying fields and forces, caused by magnetic field partly subtracting from each other. In the attached document, an IC engine magnetic flywheel described. The time averaged target torque, over 10’s of machine cycles, is used to change the reluctance of the magnetic circuit, so as to change the field strength and developed force and torque so as to reduce the ripple. In addition, dynamic mass and moment of inertia is considerably reduced, since the required forces / torques can be achieved with small Neodymium magnets. Sensor and Actuator The EEMEC comprises a sensing / controlling portion (setting the hidden variable(s)), and an actuating portion (the end-effector emec). The unique properties of EMECS enable the sensing and actuating portions to be customized to show a wide variety of input- output transformations. The sensing can yield a linear variation of sensed position P1 with respect to force / torque (within limits), a quadratic variation, etc. The actuation can in turn yield a linear variation in force / torque with respect to the sensed position P1, a quadratic variation w.r.t P1, etc. Details are in Section 4 and 7. Depending on the design of the sensor and actuator emec, all methods of modern control including proportional Integral derivative (PID), model predictive control (MPC) and others can be implemented. An emec which acts as a compensator can be installed in the control loop as per the state of art in control systems. The input-output relationships of the actuator, the controller including a compensator if needed, and the feedback loop can be customized based on the customizable electromagnetics embedded in emecs, exemplarily without the use of electronics (analog or digital). The software and hardware (i.e. the design and fabrication of the magnetics), to achieve this have not been described in the prior art. Electronic and all other existing means of active or passive control, using possibly electromagnets, can be used in combination with the methods in this description. The invention incorporating these ideas will be illustrated by certain embodiments, but the invention scope extends to all the pairs and mechanisms built from them, as described in US 7,348,754 and subsequent divisionals, and enhanced by the ideas herein. All the apparatus in Section G of the aforesaid US 7,348,754 and divisionals can be enhanced by the invention. The invention extends to all similar embodiments, wherein exemplarily the internal structure of an electrical mechanism changes, in response to the externally imposed load force / torque / velocity / …, leading to a change in the externally observable force / torque developed by the mechanism. The invention modifies the fundamental behaviour of epairs (enhanced pairs, in the terminology of US 7,348,754), by the introduction of hidden internal parameters. However, in this application, we shall continue to use the same terminology for simplicity, unless otherwise specified. A new nomenclature may be used during the national filing stage. 8.1. Feedback Dynamics As per the state of art, the feedback system bandwidth determines the tracking error for a varying external load at the end effector. In a exemplary embodiment, the external load is cyclostationary, and exhibits slow changes in the mean offered to the EEMEC, superimposed on fast cyclic changes. Exemplarily, in the case of an IC engine, the engine sequences through the intake, compression, power, and exhaust strokes for 4-stoke engines, and intake-compression and power-exhaust for 2- stroke engines. Superimposed on this high speed cyclostationary variation at 300-6000 RPM (5 to 100 Hz), or higher is a slow variation of average power output – the throttle – varying slowly with a time constant of seconds. The EEMECs sense this change in average power, and respond appropriately, as described in Sections 9, 10, 11, and 12. 8.2. Correction of Phase Error Rotating EMECS are sensitive to phase mismatches between the externally imposed cyclostationary load and the emec configuration. This is especially important in mechanisms with exhibiting highly variable forces / torques, like a magnetic flywheel coupled to an IC engine to smooth out torque ripple. The wrong phase can cause torque ripple to increase instead of decreasing. EEMECs handled this by reconfiguring the internal structure of the EEMEC, to reduce phase mismatch. This reconfiguration can be both passive or active, analogous to phase lock loops. In the case of an IC engine, the stator magnets can be shifted in angle away from Top / Bottom-Dead- Center (TDC / BDC), as shown in Figure 5 redrawn from US 7,348,754. The angular position of M_x_110, and the additional optional magnets, can be changed using an angular alignment mechanism (exemplarily a section of a worm gear – not drawn for clarity), which can be driven by another actuator. M_x_110 and the additional optional magnets are shifted slightly in angle (+ / - 5 degrees for the examples in the attached paper), to reduce phase error. It is clear that the same principles of magnetics having slightly adjustable position and orientation can be used in all portions of EEMECs. The adjustment can be at time of manufacture, as part of engine balancing, or automatically during operation, to compensate for system drift.

[0004] 9. EXTENDED EPAIRS: Sensors and Actuators Every epair can give force / torque dependent response, following the principles of the invention. However, compared to the prior art, the notion of a epair has to be modified due to the following reasons: • The behaviour is modified by a hidden configuration variable • The Interactions can be global, across multiple pairs in general. However, for purposes of nomenclature, we will continue to use the standard terminology (as in US 7348754) - prismatic pairs, revolute pair, and so on, but note that the magnetic interaction depends on the force / torque applied, and may be modulated by other pairs and / or portions of the mechanism. A new nomenclature may be incorporated during the national filing stage. 9.1. EEPAIRS as Sensors Sensing is done by movement of a emec pair in response to a external force / torque – this is not manifested in conventional (passive) mechanisms, where the mechanism unless actively powered, develops no responding force. The input-output function (i.e. position as a function of external force / torque) can be customized by a suitable design of the sensing emec – the linkage structure, and the magnetics. Exemplarily, the input-output function can be • Linear, with or without saturation • quadratic • general nonlinear Considering magnetics, from the state of art exemplarily in Wikipedia https: / / en.wikipedia.org / wiki / Force_between_magnets the force between two cylindrical magnets varies from quadratic in separation, to forth power, or higher. Inverting this, distance between two cylindrical magnets varies from the square root to the forth and higher root of the inverse of the force applied. A array of magnets of appropriate strength yields a force proportional to a general polynomial F(x) = a0 + a1 / x + a2 / x^2 + … And the distance as a function of force is the inverse map, which can be customized to suit. Considering Figure 6 magnet M12 is smaller in width than M11, and M22 is similarly smaller in width compared to M21. Similarly the distance between them, Y, is half of X, exemplarily leading to a inverse forth power variation, compared an inverse quadratic. By superposition, F(x) = K(1 / x^2 + K1 / x^4), K1 < 1 K is a normalizing constant relating inverse squared distance to force. Inverting this yields x as a function of force F. A choice of the width(s) of M12, and M22 specifies K1, and hence the inverse map x(F). These widths can be chosen to customize the map to a desired functional form - e.g the ones mentioned above. Clearly multiple magnets, appropriately positioned at varying distances, can be employed to obtain a wide variety of sensor input-output (force->distance) maps. A mechanical stop can be used to limit the position – giving saturation effects. These sensed distances are then used to drive the second emec, which responds to this change in distance, and hence indirectly responds to the externally imposed force. This facility is not present in the prior art. The same facility can be used to initialize the EEMEC to develop a targeted response to a nominal design external force / torque. The force / torque response has to be accurately synthesized, and the techniques in Section 7.1 including the auxiliary field generating electromagnet to overcome ill-conditioning can be applied. Below, embodiments of this principle for all the epairs used in emecs is described. We reiterate that the concept of a epair with a hidden configuration variable is not present in the prior art, but for simplicity of nomenclature, we use the same terms. Below we discuss the interactions in epairs having magnets, but the same can be extended to epairs having hysteresis and induction members, following the discussion in our patents 7,348,754 and subsequent ones. 9.1.1. Prismatic Epair The linear separation changes as a function of force between two magnets in a prismatic epair (one magnet on each link). The linear separation between two magnets of different prismatic epairs, sharing a common slide can also be used to sense force. 9.1.2. Revolute Epairs The angular separation changes as a function of torque transmitted between two magnets on the two components of a revolute epair, or on different revolute epairs sharing a common member - the same shaft, or the same bearing / pair of bearings. 9.1.3. Screw Epair Similar to the above, both the linear and angular separation changes as a function of force and / or torque transmitted between two magnets on the two components of a screw epair. 9.1.4. Spherical Epair Similar to the above, both the 3-D solid angle changes as a function of force and / or torque transmitted between two magnets on the same spherical epair (ball and socket joint) 9.1.5. Cylindrical Epair Similar to the above, both the angular and linear separation between two magnets connected on the same cylindrical epair changes as a function of the transmitted force / torque between them. 9.1.6. Type B Emec Here the electromagnetic interaction is global, and is not separable into interactions between members of the same epair, with limited interaction between epairs as above. Full blown Maxwell equation solvers are required. 9.2. EEPairs as Actuators Actuation is done by changing the configuration of an actuator emec, based on the change in configuration of the sensing emec. The change in configuration is in the hidden configuration variables. This is illustrated in the embodiments below, and the IC Engine example of Figure 5. 10. Modulation of Induction Force 10.1. Extended Prismatic Pair EEMECS can function as an induction brake sensitive to both driving force and velocity (not velocity only), while remaining a passive system without active electromagnets. Here developed induction force is modulated. One embodiment uses two magnets repelling each other on a common guide, as shown in Figure 8. These comprise two pairs interacting with each other, a feature not present in the prior art. In the terminology of mechanisms, and specifically 7,348,754, two different enhanced pairs interact here – each pair being enhanced by the addition of inductive forces between the induction member and the magnet M1 and M2. The interaction between the two different epairs is magnetic, and not inductive. This is a form of global interaction between different epairs, of different types (one interaction between inductive, and another being magnetic repulsion), and is not in the prior art. The distance between the two magnets decreases with increased force Fapplied, leading to a smaller air gap (which includes the induction member as shown), higher flux in the magnetic circuit, and higher braking at the same speed, at the same position x of the left magnet (to which the external force is applied. M2 and M1 are collinear with each other, and M2 is rigidly connected to steel flux return path SF1 – an detailed MCAD drawing will be furnished in an amendment or during the national stage). Figure 9 shows more details. It is important to note that the steel flux return path SF1 in this example varies in thickness as a function of position x, leading to force produced varying with position x. However, in the state-of-art and our earlier patents, at a given position x, the force is constant, and independent of the applied external force Fapplied. The position of the right magnet M2, (say y) is a hidden internal variable, from the external world. It changes as a function of applied force / torque, leading to the prismatic pair changing its braking force at the same x, and the same velocity. The braking force is changing as a function of external force / torque. This is a prismatic pair, enhanced with force dependent braking. Other configurations exist, e.g.with three magnets M1, M2, and M3, with M1 and M2 setting the flux return path reluctance, and a separate magnet M3 developing the induction flux (M3 does not interact directly with the load). A MCAD drawing will be furnished, as an amendment or before national phase entry.

[0005] In essence, the mechanism reconfigures itself like a centripetal speed governor, or a governor with springs. Here instead of centripetal or elastic forces, we have magnetic forces, which can be attractive, repulsive, show hysteresis and induction, …. In addition, electromagnets can be used in conjunction, for further control. Feedback control is applied by the change in geometry caused by the external force / torque. The same ideas can be applied to all pairs, discussed at length in US 7,348,754, (Figure 24, 25, …, 36, and others) and results in the entire mechanism changing its dynamics as a function of force / torque applied at the end effector or effectors (if there are multiple end-effectors). It can also be applied to clusters of epairs. 10.2. Error Signal An EEMEC is a feedback control system. The error signal can be identified with the difference between the separation between the two magnets M1 and M2, and a reference distance, corresponding to a nominal force. Figure 10 shows how the change of the airgap between two magnets yields an error signal – forces between M1 and M2 greater than nominal Fnominal reduce the air gap, with the reduction being reckoned as a negative increment ΔX<0, and forces less than nominal increase the air gap, with a positive ΔX>0. This change from nominal is an error signal changing the structure of the actuator mechanism and changes exemplarily the air gap in magnetic circuits conveying the flux (the magnetic circuit in Figure 8 is formed by the two magnets, the steel flux return path S1 at the top, and the induction member I1 at the bottom. As mentioned in Section 9.1, the error signal can be linear with / without saturation, quadratic, etc, w.r.t force. The error signal can change other aspects of the mechanism also, Including the positions of the induction and autonomously magnetic members. All methods of feedback control, PID, MPC. etcetera can be applied based on the error signal. As mentioned above, the same facility to set the flux path reluctance can be applied to initialize the EEMEC to generate a nominal braking force at a nominal impressed force and velocity. We note that the internal mechanism of this EEPAIR operates by changing flux path reluctance, but the external dynamic impact is by changing induction force. 11. Modulation of Flux Path Reluctance 11.1. Extended Revolute Pair Figure 11 shows the same concept for a revolute pair (actually a couple of pairs, located on the same shaft), where the flux path reluctance is modulated. In this example, we have torque dependent flux reluctance, leading to change in the net reaction torque produced by the actuator emec (not shown). For specificity, Figure 11 above shows the shafts and a portion of the magnetic circuits corresponding to Fig 36 of US 7348754 (IC Engine). The magnetic circuit (shown as the double sided arrow in Figure 11) connects to stator and rotor magnets as per Fig 36 of US 7348754 (the complete magnetic circuit and magnets are not shown for clarity). In this configuration, the two angular sectors at angle Theta1 from each other, do not overlap – in other configurations they do. The magnetic circuit passes from one of the angular sectors, to the other. The angular sectors are held in their position, by a torsion / magnetic springs, at an angle Theta1 depending on the applied torque. Hence the overlap between the two angular sectors, one connected to the rotor magnets and another to the stator magnets, determines the total reluctance of the magnetic circuit, and hence the magnetic field strength, and force / torque produced. When this system is used as part of the flux return reluctance path of a magnetic flywheel, it can offer varying smoothing torque, depending on the applied torque (filtered by the system dynamics). However, there are multiple configurations for the same developed torque and the mechanism has to be carefully designed to deterministically pick one of these configurations – a random choice is generally undesirable. In addition to residual low power active control, where only one configuration is actively selected, a purely passive means of achieving this is presented in Section 11.2 below. 11.2. Configurational Hysteresis Effects As the load varies, the internal configuration itself changes (due to change Theta1, leading to change in overlap between the two angular sectors). This results in configurational hysteresis which has to be properly handled. The hysteresis introduces multiple combinations of hidden and externally visible state developing the same torque. Theta1 or Theta2 or both can decrease, bringing the magnets in the rotor and stator (as per Figure 34 or 7,348,754) closer (Theta 1 decrease), or closer to the stator magnets (Theta 2 decrease). There are multiple choices of Theta1 and Theta2 yielding the same torque. The trajectory in the joint space of [observable, hidden] parameters, here [Theta1, Theta2] has to be carefully controlled. One means of doing this is by utilizing the (already present) mechanical inertia in the system. In Figure 12, the torque developed increases from T1, and T2 > T1. Due to the mechanical inertia, the angular separation between the rotor and stator sectors, Theta1 will be almost constant, and the trajectory in the Theta1, Theta2, plane will be almost vertical, for fast changes in average torque. A magnetic flywheel EEMEC hence exhibits a slow change in developed average force while retaining the cyclostationary magnetic force profile, by modulation exemplarily of flux path reluctance. The cyclostationarity is due to the inbuilt geometric arrangement of the stator magnets, interacting with rotating rotor magnets.

[0006] Previous patents are static, and the geometry of the system does not change as a function of speed, force / torque / … 12. Modulation of Magnetic Field Strength 12.1. Extended Revolute Pairs The field changes as the separation between the two magnets in either Figure 9, or Figure 11 changes, and this aspect will not be separately discussed here. However, an independent effect is the change in the field geometry, due to change in magnet positioning (independent of the flux reluctance path changes). All this changes the force / torque developed, and can be used throughout an EEMEC. Other examples may be furnished in Article 34 amendments or the national phase. 13. Other Pairs The same principles can be applied to all pairs – the revolute pair, the screw pair, the spherical pair, … and by implication, an entire EEMEC. 14. Internal Hidden and External Observable Parameters

[0007] A few other illustrations of EEMECS are furnished in this application. In Figure 13 the external force torque causes the hidden parameters to change and at the same combination of observable parameters the response to the external force torque changes. A general exemplary structure of an EEMEC is shown in Figure 14. 15. Composition of Extended epairs to yield extended emecs (EEMECs). The extended epairs can be joined together, to form full EEMECs. The geometric structure and kinematics is identical to standard mechanism, but the dynamics can be completely different, and designed as desired, due to the electromagnetic energy present in the mechanism. In addition, interactions occur not just within a single epair, but also between different epairs, which is not present in the prior art. 16. Apparatus using the invention Based on the description above, all the apparatus mentioned in US 7,348,754 can be enhanced by the invention (including but not limited to those in Section G). A few exemplary examples are below. These directly refer to the corresponding apparatus in 7,348,754, and the corresponding figures. • A toothbrush, whose force of brushing changes, depending on the force used to press the toothbrush against the tooth. • A well pulley, whose braking torque at the same rotational speed, increases as the load increases, using sensing and controlling mechanism M1 to increase the field by reducing the airgap, and hence the braking force at the same speed. • An IC-engine magnetic flywheel, where the torque ripple can be smoothed out even as throttle varies. Note that the required change in the EEMEC (magnetics, including flux return path) can be manually initiated, by the accelerator pedal also. • The stepper mechanism of Figure 30 of 7,348,754, where the holding torque at each step can be changed, depending on the sensed load, without the use of electronic circuitry. • A bubble vibration toy (BVT), where the driving force changes depending the viscosity of the soap film. An EEMEC driving a BVT can also deliver carefully controlled vibrations of the soap film frame, with spatial nodes moved around, causing delightful rotation of standing waves / shapes.

Claims

CLAIMS 1. We claim an emec where the force / torque produced, changes depending on the force / torque applied by an external entity and o The change in force / torque from a nominal force / torque, produced depends on the difference between a target force / torque and the achieved force / torque, and the said change is produced by changing the structural parameters of one or more hidden elements of the magnetic circuits present in the mechanism o Where the same said changeable force / torque is used to initialize the EEMEC to deliver a nominal force / torque at a nominal external impressed force / torque at one or more end- effectors.

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