Force feedback system and force feedback control method

Abstract

The invention relates to the technical field of force feedback, and provides a force feedback system and a force feedback control method. The force feedback system comprises a force feedback device, the force feedback device comprises multiple sets of force feedback mechanisms, the multiple sets of force feedback mechanisms are arranged in a pairwise orthogonal mode, the moving directions of the multiple sets of force feedback mechanisms are perpendicular to one another, and each set of force feedback mechanism comprises a permanent magnet and a moving assembly, when the permanent magnet rotates, the moving assembly can be driven to move, so that torque borne by the permanent magnet is converted into force in the linear direction. According to the force feedback system, the multiple sets of force feedback mechanisms are arranged, and the multiple sets of force feedback mechanisms are arranged in a pairwise orthogonal mode, so that an operator can feel force in the directions of multiple degrees of freedom; the permanent magnets are arranged in each group of force feedback mechanisms, the torque of the permanent magnets is converted into feedback force, and the working space of the force feedback system is increased by utilizing the characteristic that the space attenuation of the electromagnetic torque is far smaller than that of the electromagnetic force.

Description

Technical Field

[0001] This invention relates to the field of force feedback technology, and in particular to a force feedback system and a force feedback control method. Background Technology

[0002] Currently, many force feedback systems are designed based on the principle of electromagnetic force. Specifically, there are systems based on a single spherical electromagnet, which consists of a spherical iron core and three orthogonal coils, possessing three degrees of freedom in force. Users need to hold a pen-like tool containing a permanent magnet close to the electromagnet to feel the force generated, thus enabling tactile perception of virtual objects in virtual reality / augmented reality (VR / AR) systems. Another example is a force feedback system composed of a 3x3 electromagnetic coil planar array; users need to wear finger cots with permanent magnets to perceive virtual objects. Yet another example is a force feedback system composed of a 15x15 electromagnetic coil planar array, used for perceiving virtual objects. In this magnet array, each magnet is surrounded by a flux concentration layer to enhance the magnetic field strength in the operating space. Outside the concentration layer is an isolation layer to ensure that the magnetic fields generated by the magnets in the array do not interfere with each other.

[0003] The aforementioned electromagnetic force feedback systems suffer from several limitations. Firstly, the electromagnetic force weakens rapidly with increasing workspace. Secondly, the limited heat generation capacity restricts the workspace available to generate sufficient feedback force for human perception (within 1-3 cm of the electromagnet). This significantly restricts the operator's movement. Furthermore, the degrees of freedom provided by these electromagnetic force feedback systems often do not cover the entire three-dimensional space, and their feedback accuracy is also quite limited. Summary of the Invention

[0004] This invention provides a force feedback system and a force feedback control method to solve the defects of existing force feedback systems, such as small working space and few degrees of freedom of feedback force.

[0005] The present invention provides a force feedback system, including a force feedback device, wherein the force feedback device includes multiple sets of force feedback mechanisms, the multiple sets of force feedback mechanisms are arranged orthogonally in pairs, and the moving directions of the multiple sets of force feedback mechanisms are perpendicular to each other. Each set of force feedback mechanisms includes a permanent magnet and a moving component. When the permanent magnet rotates, it can drive the moving component to move, so as to convert the torque on the permanent magnet into a force in a linear direction.

[0006] According to a force feedback system provided by the present invention, the moving component includes: a gear, coaxially arranged with the permanent magnet, which can drive the gear to rotate when the permanent magnet rotates; and a rack, which meshes with the gear.

[0007] According to a force feedback system provided by the present invention, each group of force feedback mechanisms further includes:

[0008] A baffle is connected to the rack, the rack has a protrusion, and the protrusion is parallel to the baffle; a limiting block is located between the protrusion and the baffle.

[0009] According to a force feedback system provided by the present invention, an electromagnet array is further included, the electromagnet array being hemispherical, the electromagnet array being used to provide a magnetic field for the permanent magnet.

[0010] According to a force feedback system provided by the present invention, the electromagnet array includes multiple layers of electromagnets, the number of layers of electromagnets is odd, the multiple layers of electromagnets are symmetrically distributed with the middle layer as the axis of symmetry, and the number of electromagnets in each layer decreases along the direction extending from the middle layer to both sides.

[0011] According to a force feedback system provided by the present invention, a driving device is further included, the driving device comprising: a controller and a plurality of control mechanisms, the controller being electrically connected to the plurality of control mechanisms, and each of the control mechanisms being electrically connected to one electromagnet in the electromagnet array.

[0012] According to a force feedback system provided by the present invention, each of the control mechanisms includes: a generator, a current controller, and a current sensor. The generator is electrically connected to the controller and the current controller. The controller adjusts the actual current of each electromagnet in the electromagnet array by adjusting the duty cycle of the generator. The current sensor is used to detect the actual current of one of the electromagnets.

[0013] According to a force feedback system provided by the present invention, it further includes: a host and a positioning device, wherein the host is used to acquire a target force, the positioning device is used to acquire the position of the force feedback device, and both the host and the positioning device are electrically connected to the controller.

[0014] The present invention provides a force feedback control method based on the force feedback system described above, comprising: acquiring a target force and the position of the force feedback device; calculating a target current for each electromagnet in the electromagnet array based on the target force and the position of the force feedback device; adjusting the actual current of the electromagnet based on the target current, and making the difference between the actual current and the target current less than a threshold.

[0015] According to the force feedback control method provided by the present invention, the step of adjusting the actual current of the electromagnet based on the target current and making the difference between the actual current and the target current less than a threshold includes: adjusting the duty cycle of the corresponding generator based on each target current; acquiring the actual current of each electromagnet; comparing the actual current with the target current, and if the difference between the actual current and the target current is greater than or equal to the threshold, adjusting the duty cycle of the generator again; acquiring the actual current of each electromagnet again, and comparing the actual current with the target current again, until the difference between the actual current and the target current of each electromagnet is less than the threshold.

[0016] The force feedback system provided by this invention, by setting up multiple sets of force feedback mechanisms, with each set of mechanisms arranged orthogonally in pairs, allows the operator to feel forces in multiple degrees of freedom. By setting permanent magnets in each set of force feedback mechanisms, the torque of the permanent magnets is converted into feedback force. Taking advantage of the characteristic that the spatial attenuation of electromagnetic torque is much smaller than that of electromagnetic force, the working space of the force feedback system is increased. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0018] Figure 1 This is one of the structural schematic diagrams of the force feedback device in the force feedback system provided by the present invention;

[0019] Figure 2 This is the second schematic diagram of the structure of the force feedback device in the force feedback system provided by the present invention;

[0020] Figure 3 This is a structural diagram of the moving component;

[0021] Figure 4 This is a schematic diagram of the electromagnet array in the force feedback system provided by the present invention;

[0022] Figure 5 This is a schematic diagram of the structure of the driving device in the force feedback system provided by the present invention;

[0023] Figure 6 This is a schematic diagram of the force feedback system provided by the present invention;

[0024] Figure label:

[0025] 10: Force feedback device; 11: Baffle; 12: Limiting block; 13: Gear; 14: Rack; 15: Permanent magnet; 16: Bearing; 17: Shaft; 18: Frame; 20: Electromagnet array; 21: Electromagnet; 31: Controller; 32: Generator; 33: Current controller; 34: Current sensor; 40: Main unit; 50: Positioning device; 141: Protrusion. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0027] The terms "first" and "second" in the specification and claims of this invention may explicitly or implicitly include one or more of those features. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0028] The following combination Figures 1-6 The force feedback system and force feedback control method of the present invention are described.

[0029] like Figure 1 As shown, in an embodiment of the present invention, the force feedback system includes a force feedback device 10, which includes multiple sets of force feedback mechanisms. The multiple sets of force feedback mechanisms are arranged orthogonally in pairs, and the moving directions of the multiple sets of force feedback mechanisms are perpendicular to each other. Each set of force feedback mechanisms includes a permanent magnet 15 and a moving component. When the permanent magnet 15 rotates, it can drive the moving component to move, so as to convert the torque received by the permanent magnet 15 into a force in a linear direction.

[0030] Specifically, the force feedback device 10 includes a frame 18, within which multiple sets of force feedback mechanisms are housed. There can be two or three sets of force feedback mechanisms, each capable of movement in one direction, thus giving the force feedback device 10 two or three degrees of freedom. In this embodiment, for a permanent magnet 15 located at point P, assuming an external magnetic field B(P) exists at that point and the magnetic dipole moment of the permanent magnet 15 is m, the permanent magnet 15 will experience a torque τ, the magnitude of which satisfies the formula: τ = m × B(P).

[0031] As the formula shows, torque cannot contain a component parallel to the magnetic dipole moment; therefore, the direction of this magnetic moment is always confined to a two-dimensional plane perpendicular to the magnetic dipole moment of the permanent magnet 15. To convert torque into force that is perceptible to the user, the rotational motion of the permanent magnet 15 under torque is transformed into linear motion. From the perspective of simplifying control and structural design, the permanent magnet 15 is restricted to rotating under torque in only one dimension, so that each permanent magnet 15 provides only one-dimensional force. To allow the operator to experience three-dimensional force, in this embodiment, there are three sets of force feedback mechanisms, arranged orthogonally in pairs.

[0032] Furthermore, the three sets of force feedback mechanisms are arranged orthogonally in pairs, meaning that the magnetic dipole moments of the three permanent magnets 15 are mutually orthogonal. This implies that each component of the magnetic field along the three orthogonal directions on the surface of the force feedback device 10 can affect the rotation of only one permanent magnet 15. To generate a force in a certain dimension, only a one-dimensional magnetic field in the corresponding dimension needs to be provided. The permanent magnet 15 rotates under the action of the magnetic field, thereby driving the moving component to move and converting torque into a force in a linear direction. When the moving component moves, the user stops it by pressing. When the moving component stops moving, the force feedback device 10 is in a balanced state. At this time, the moving component exerts pressure on the user's hand, and this pressure is the feedback force, which is equal to the force converted from the torque on the permanent magnet 15. Since the spatial attenuation of electromagnetic torque is much smaller than that of electromagnetic force, the working space of the force feedback system provided in this embodiment of the invention can be much larger than that of the electromagnetic force feedback system.

[0033] The force feedback system provided in this embodiment of the invention, by setting up multiple sets of force feedback mechanisms, with each set of force feedback mechanisms arranged orthogonally in pairs, allows the operator to feel forces in multiple degrees of freedom directions; by setting a permanent magnet in each set of force feedback mechanisms, the torque of the permanent magnet is converted into feedback force, and by utilizing the characteristic that the spatial attenuation of electromagnetic torque is much smaller than that of electromagnetic force, the working space of the force feedback system is increased.

[0034] like Figure 2 and Figure 3 As shown, in an embodiment of the present invention, the moving component includes a gear 13 and a rack 14. The gear 13 is coaxially arranged with the permanent magnet 15, and the permanent magnet 15 can drive the gear 13 to rotate when it rotates. The rack 14 meshes with the gear 13.

[0035] Specifically, in embodiments of the present invention, the moving assembly further includes a bearing 16 and a rotating shaft 17. The gear 13 and the permanent magnet 15 are coaxially arranged via the bearing 16 and the rotating shaft 17. The permanent magnet 15 rotates under the influence of the magnetic field, thereby driving the gear 13 to rotate. When the gear 13 rotates, it presses against the rack 14, converting the torque into a force in a linear direction. The converted force and torque satisfy the following relationship:

[0036] ||τ||=||F||R, where F is the force converted from torque and R is the radius of the 13-pitch circle of the gear.

[0037] like Figure 1 As shown, in an embodiment of the present invention, each force feedback mechanism further includes a baffle 11 and a limiting block 12. The baffle 11 is connected to a rack 14, and the rack 14 is provided with a protrusion 141, which is parallel to the baffle 11. The limiting block 12 is located between the protrusion 141 and the baffle 11.

[0038] Specifically, the limiting block 12 is disposed within the frame 18, and one or both ends of the rack 14 are respectively connected to baffles 11, allowing the rack 14 to drive the baffles 11 to move along the frame. In this embodiment, baffles 11 are connected to both ends of the rack 14. When the gear 13 is not rotating, the baffles 11 on both sides of the rack 14 are located in two opposite surfaces of the frame 18. When the gear 13 rotates, the baffles 11 move along the frame 18 and eventually abut against the limiting block 12. When the gear 13 rotates in the opposite direction, the protrusion 141 moves with the rack 14 and eventually abuts against the limiting block 12. That is, in this embodiment, the limiting block 12 is used to limit the movement of the baffles 11 and the protrusion 141. In this embodiment, the user needs to press down on the baffles 11 by hand before the baffles 11 abut against the limiting block 12 or before the baffles 11 abut against the protrusion 141. When the baffle 11 stops moving and does not contact the limit block 12, the force feedback device 10 is in a force balance state. At this time, the baffle 11 exerts pressure on the user's hand, and this pressure is equal to the torque conversion force F.

[0039] like Figure 4 As shown, in an embodiment of the present invention, the force feedback system further includes an electromagnet array 20, which is hemispherical and is used to provide a magnetic field for the permanent magnet 15.

[0040] Specifically, the electromagnet array 20 is set as a hemisphere, that is, the axis of each electromagnet 21 is oriented towards the center of the array, and all electromagnets 21 are symmetrically distributed with respect to the diameter of the sphere formed by the array. This design is intended to ensure an approximately uniform magnetic field distribution in all directions in three-dimensional space, and also to allow space for the user's hand to be inserted during actual operation.

[0041] Furthermore, in an embodiment of the present invention, the electromagnet array 20 includes multiple layers of electromagnets 21, the number of layers of electromagnets 21 is odd, the multiple layers of electromagnets are symmetrically distributed with the middle layer as the axis of symmetry, and the number of electromagnets in each layer decreases along the direction extending from the middle layer to both sides.

[0042] Specifically, each electromagnet 21 consists of a coil and an iron core wrapped by the coil. In embodiments of the invention, cylindrical electromagnets 21 are chosen because their cylindrical shape allows the generated magnetic field to be symmetrical in the radial direction. The shape of the cylindrical electromagnet 21 is determined by the following geometric parameters: the outer radius R of the coil... out Coil inner radius R in Core radius R core 1. Electromagnet length L, 2. Coil wire diameter d.

[0043] To maximize the magnetic field strength, there is generally no gap between the coil and the iron core, therefore R in =R core With other parameters remaining constant, increase R. out Both L and R can increase the number of turns in an electromagnet coil, thereby increasing the strength of the generated magnetic field. However, R... out An excessively large coil will result in excessive coil thickness, making heat dissipation difficult, increasing energy consumption, and affecting performance. Furthermore, R... out The volume of L also affects the overall volume of the cylindrical electromagnet 21. Considering the requirements of practical applications, the volume of the electromagnet 21 should not be too large. out The values ​​of R and L should also be within a suitable range. For the coil wire diameter d, assuming other geometric parameters and a constant current through a single turn, a smaller diameter results in more turns, a higher current density, and theoretically, a larger magnetic field generated by the electromagnet 21. However, an excessively small d will increase the overall resistance of the coil, leading to increased heat generation and negatively impacting the overall performance of the electromagnet 21. Therefore, for coils wound with copper wire, d should be in the range of 0.6–1 mm. In this embodiment, R… out =25mm, L=50mm, d=0.7mm.

[0044] For the inner diameter R of the coil in As far as R is concerned, in If it's too small, the iron core will be too small, resulting in insufficient magnetic field generated by the iron core; while R in If the coil volume is too large, and the number of turns is too small, the external magnetic field of the magnetized iron core (i.e., the magnetic field generated by the coil itself) will be too small, resulting in insufficient magnetic field generated by the iron core. Therefore, when other parameters remain constant, there exists a value R. in To maximize the magnetic field produced by electromagnet 21, finite element analysis was used to determine R, which maximizes the magnetic field. in Value, R in-max =10mm. Considering that the coil thickness should not be too large, R was ultimately... in Set to 15mm. Compared to 10mm, R inThe magnetic field generated by 15mm is reduced by only 7%, but it can significantly reduce the coil thickness, thereby reducing the heat dissipation pressure of the electromagnet array 20, which is an acceptable compromise.

[0045] Regarding the number, array radius, and arrangement of electromagnets 21, it is necessary to use finite element analysis and numerical calculation methods during the design process to compare the magnetic field control capabilities of electromagnet arrays 20 with different numbers of electromagnets 21, array radii, and arrangements, and select the array with the strongest magnetic field control capability as the final design.

[0046] The measure of electromagnetic field control capability is the minimum singular value σ obtained after singular value decomposition of the transition matrix B(P) between current and electromagnetic field. min ,Right now Where B(P) = [B1(P, 1) B2(P, 1)...B n [P, 1] is the transition matrix between the current and the electromagnetic field of the electromagnet array.

[0047] B i (P, 1) = [B ix (P, 1) B iy (P, 1) B iz [P, 1)] (i = 1, 2, ..., n) represents the position P = [x, y, z] of the i-th electromagnet 21 in an array of n electromagnets 21 when a unit current passes through it. T The magnetic field strength generated at point B i (P, 1) can generally be obtained through direct calculation (including analytical and numerical methods), finite element simulation, or direct measurement of the electromagnet array 20. σ i (i = 1, 2, ..., n) are the singular values ​​obtained from the singular value decomposition of the transition matrix. σ min The smaller the value, the worse the magnetic field control capability of the electromagnet array 20.

[0048] After comparison, the final array consists of 13 electromagnets 21 with a radius of 100 mm. The electromagnets 21 in the array can be divided into five layers. The middle layer (third layer) includes five electromagnets 21 with their axes on the horizontal plane, and the angle between the axes of adjacent electromagnets 21 is 45 degrees. The second and fourth layers are symmetrical about the horizontal plane, each containing three electromagnets 21, and the projection angle of the axes of adjacent electromagnets 21 onto the horizontal plane is also 45 degrees. The first and fifth layers each contain one electromagnet 21, with the two electromagnets 21 symmetrical about the horizontal plane, and their axes perpendicular to the horizontal plane. This electromagnet array 20 has good magnetic field control capability at any position within its working space.

[0049] For an electromagnet array 20, its spatial magnetic field distribution is equal to the vector sum of the spatial magnetic field distributions generated by each electromagnet 21 in the array, that is:

[0050] B(P,I)=B1(P,I1)+B2(P,I2)+...+B n (P, I) n ), where B(P, I) is the magnetic field strength at any point P in space, and I = [I1 I2 ... I n ] T Let I be the current vector of the electromagnet array, where I1, I2, ..., I... n These represent the currents passing through the 1st, 2nd, ..., nth electromagnets in an electromagnet array 20 containing n electromagnets 21.

[0051] B1(P,I1),B2(B,I2),...,B n (P, I) n The numbers ) represent the currents I1, I2, ..., In passing through the 1st, 2nd, ..., nth electromagnets 21, respectively. n The strength of the magnetic field generated at that point. Furthermore, for each electromagnet 21, there is a linear relationship between the current flowing through it and the strength of the magnetic field generated, that is, the strength of the generated magnetic field is equal to the magnetic field strength generated per unit current multiplied by the current magnitude: B i (P, I) i ) = B i (P, 1)I i Where i = 1, 2, ..., n, therefore, the above equation can be expressed in matrix form as B(P, I) = B(P)I.

[0052] Furthermore, since the geometric parameters and materials of each electromagnet 21 in the electromagnet array 20 are identical, differing only in their position and orientation within the array, to simplify calculations, we can first obtain the spatial distribution of the magnetic field strength of each electromagnet 21 under a unit current within the coordinate system formed by each electromagnet 21. Then, we can perform a coordinate system transformation to obtain the spatial distribution of the magnetic field strength of each electromagnet 21 within the array's coordinate system. O B i ( O P, 1): Where O represents the array coordinate system and i represents the coordinate system of the i-th electromagnet; i B i ( i P,1) represents the spatial distribution of the magnetic field strength in the coordinate system of the i-th electromagnet, and this distribution is the same for each electromagnet. Let be the transformation matrix from the coordinate system i of the i-th electromagnet to the array coordinate system O. Since for each electromagnet iBi ( i Since P and 1) are the same, the amount of computation can be greatly reduced by using the coordinate transformation method.

[0053] like Figure 5 As shown, the force feedback system also includes a drive device, which comprises a controller 31 and multiple control mechanisms. The controller 31 is electrically connected to the multiple control mechanisms, and each control mechanism is electrically connected to an electromagnet 21 in the electromagnet array 20. The controller 31 is used to calculate the target current based on the target force and adjust the actual current of the electromagnet 21 in the electromagnet array 20 by adjusting the duty cycle of the control mechanisms. The control mechanisms detect the actual current of the electromagnet 21, and when the difference between the actual current and the target current is greater than or equal to a threshold, they continue to adjust the duty cycle until the difference between the actual current of the electromagnet 21 and the target current is less than the threshold.

[0054] Furthermore, each control mechanism includes a generator 32, a current controller 33, and a current sensor 34. The generator 32 is electrically connected to the controller 31 and the current controller 33. The controller 31 adjusts the actual current of the electromagnet 21 by adjusting the duty cycle of the generator 32. The current sensor 34 is used to detect the actual current of the electromagnet 21.

[0055] Specifically, to ensure the generated magnetic field strength reaches a preset value, the current flowing through each coil in the electromagnet array 20 needs to be accurately controlled. In this embodiment, the controller 31 receives instructions and, via the I2C communication protocol, writes a PWM duty cycle to the generator 32, which controls the current of a specific electromagnet 21, to achieve the target current. Based on this duty cycle, the generator 32 generates a corresponding PWM signal, and the current controller 33 then generates a certain current input to the electromagnet coil based on the received PWM signal.

[0056] Since the relationship between the PWM duty cycle and the coil current is not fixed and is affected by various external factors, it is necessary to implement feedback control of the coil current. To this end, a current sensor 34 is installed in the drive unit to achieve precise current control. The current sensor 34 detects the magnitude of the coil current and returns this value to the controller 31. The controller 31 compares the target current with the actual current detected by the current sensor 34, and then increases or decreases the duty cycle value written to the generator 32. This cycle continues until the difference between the actual current detected by the current sensor 34 and the target current is less than a threshold, at which point the controller 31 stops changing the output PWM duty cycle.

[0057] Optionally, in an embodiment of the present invention, generator 32 is a PWM generator.

[0058] like Figure 6As shown, the force feedback system provided in this embodiment of the invention further includes a host 40 and a positioning device 50. The host 40 is used to acquire the target force, and the positioning device 50 is used to acquire the position of the force feedback device 10. Both the host 40 and the positioning device 50 are electrically connected to the controller 31.

[0059] Specifically, the host 40 obtains the target force by receiving instructions from other systems or user input and sends this value to the controller 31. The positioning device 50 obtains the position, i.e., coordinates, of the force feedback device 10 in the force feedback system and sends these coordinates to the controller 31. After receiving the target force and the coordinates of the force feedback device 10, the controller 31, combining the principle of the force feedback device 10 and the magnetic field control algorithm of the electromagnet array 20, calculates the current required to pass through each electromagnet coil in the electromagnet array 20, and controls it through the drive device, so that the electromagnet array 20 can quickly and accurately generate the required magnetic field strength, thereby making the feedback force applied by the force feedback device 10 to the user as close as possible to the target force.

[0060] Specifically, after obtaining B(P), using the coordinates P of the point to be controlled (i.e., the coordinates of the force feedback device 10) and the desired magnetic field strength B(P, I) at that point as input, the current I that should pass through the electromagnet array 20 can be obtained by calculating the pseudo-inverse of the matrix B(P). in Let I be the pseudo-inverse of matrix B(P). The solution obtained by this method has the least L2 norm among all solutions, which, for this force feedback system, minimizes the heat power generated by the current passing through the coil.

[0061] The force feedback system provided in this embodiment of the invention, by setting up a host, a positioning device and a driving device, can calculate the target current based on the target force. By adjusting the duty cycle of the generator, the actual current of each electromagnet in the electromagnet array is made close to the target current, so that the magnetic field strength generated by the electromagnet array reaches a preset value. Under this magnetic field strength, the feedback force of the force feedback device is close to the target force, thereby improving the accuracy of the feedback force output.

[0062] This invention also provides a force feedback control method based on a force feedback system, specifically including the following steps:

[0063] Step 01: Obtain the target force and the position of the force feedback device 10; Step 02: Based on the position of the target force and the force feedback device 10, calculate the target current of each electromagnet 21 in the electromagnet array 20; Step 03: Adjust the actual current of the electromagnet 21 based on the target current, and make the difference between the actual current and the target current less than a threshold.

[0064] Specifically, the host 40 obtains the target force by receiving instructions from other systems or user input and sends this value to the controller 31. The positioning device 50 obtains the position, i.e., coordinates, of the force feedback device 10 in the force feedback system and sends these coordinates to the controller 31. After receiving the target force and the coordinates of the force feedback device 10, the controller 31, combining the principle of the force feedback device 10 and the magnetic field control algorithm of the electromagnet array 20, calculates the current that needs to pass through each electromagnet coil in the electromagnet array 20, and controls it through the drive device to make the actual current of each electromagnet 21 in the electromagnet array 20 close to the target current, so that the magnetic field strength generated by the electromagnet array 20 reaches the preset value, thereby making the feedback force applied by the force feedback device 10 to the user as close as possible to the target force.

[0065] Further, in an embodiment of the present invention, the step of adjusting the actual current of the electromagnet 21 based on the target current and making the difference between the actual current and the target current less than a threshold includes: adjusting the duty cycle of the corresponding generator 32 based on each target current; acquiring the actual current of each electromagnet 21; comparing the actual current with the target current, and if the difference between the actual current and the target current is greater than or equal to the threshold, adjusting the duty cycle of the generator 32 again; acquiring the actual current of each electromagnet 21 again, and comparing the actual current with the target current again, until the difference between the actual current and the target current of each electromagnet 21 is less than the threshold.

[0066] Specifically, the controller 31 calculates the target current for each electromagnet 21 in the electromagnet array 20 based on the target force and the position of the force feedback device 10, and writes the PWM duty cycle that will cause the current of a particular electromagnet 21 to reach the target current to the generator 32, which is responsible for controlling the current of a particular electromagnet 21, via the I2C communication protocol. Based on this duty cycle, the generator 32 generates a corresponding PWM signal, and the current controller 33 generates a certain current input to the electromagnet coil based on the received PWM signal.

[0067] The current sensor 34 detects the magnitude of the coil current and returns this value to the controller 31. The controller 31 compares the target current with the actual current detected by the current sensor 34, and then increases or decreases the duty cycle value of the generator 32. This cycle continues until the difference between the actual current detected by the current sensor 34 and the target current is less than a threshold, at which point the controller 31 stops changing the output PWM duty cycle. When the difference between the actual current and the target current is less than the threshold, the magnetic field strength generated by the electromagnet array 20 can make the force obtained by the torque conversion of the permanent magnet 15 in the force feedback device 10 close to the target force. Since the force obtained by torque conversion is equal to the feedback force, the feedback force can be made close to the target force, thus achieving precise control of the feedback force output.

[0068] The force feedback control method provided in this invention can calculate the target current based on the target force. By adjusting the duty cycle of the generator, the actual current of each electromagnet in the electromagnet array is made close to the target current, thereby making the magnetic field strength generated by the electromagnet array reach a preset value. Under this magnetic field strength, the feedback force of the force feedback device is close to the target force, thus improving the accuracy of the feedback force output.

[0069] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A force feedback system, characterized in that, The device includes a force feedback device comprising multiple sets of force feedback mechanisms arranged orthogonally in pairs, with the moving directions of the multiple sets of force feedback mechanisms perpendicular to each other. Each set of force feedback mechanisms includes a permanent magnet and a moving component. When the permanent magnet rotates, it can drive the moving component to move, so as to convert the torque on the permanent magnet into a force in a linear direction.

2. The force feedback system according to claim 1, characterized in that, The moving component includes: A gear is coaxially arranged with the permanent magnet, and the rotation of the permanent magnet can drive the gear to rotate. A rack meshes with the gear.

3. The force feedback system according to claim 2, characterized in that, Each set of force feedback mechanisms also includes: A baffle is connected to the rack, and the rack is provided with a protrusion that is parallel to the baffle. A limiting block is located between the protrusion and the baffle.

4. The force feedback system according to claim 1, characterized in that, It also includes an electromagnet array, which is hemispherical and is used to provide a magnetic field for the permanent magnet.

5. The force feedback system according to claim 4, characterized in that, The electromagnet array comprises multiple layers of electromagnets, the number of layers of electromagnets is odd, the multiple layers of electromagnets are symmetrically distributed with the middle layer as the axis of symmetry, and the number of electromagnets in each layer decreases along the direction extending from the middle layer to both sides.

6. The force feedback system according to claim 4, characterized in that, It also includes a drive device, which comprises a controller and a plurality of control mechanisms, the controller being electrically connected to the plurality of control mechanisms, and each of the control mechanisms being electrically connected to one of the electromagnets in the electromagnet array.

7. The force feedback system according to claim 6, characterized in that, Each of the control mechanisms includes: a generator, a current controller, and a current sensor, wherein the generator is electrically connected to the controller and the current controller, and the controller adjusts the actual current of each electromagnet in the electromagnet array by adjusting the duty cycle of the generator; The current sensor is used to detect the actual current of one of the electromagnets.

8. The force feedback system according to claim 6, characterized in that, Also includes: The system includes a host computer and a positioning device. The host computer is used to acquire the target force, and the positioning device is used to acquire the position of the force feedback device. Both the host computer and the positioning device are electrically connected to the controller.

9. A force feedback control method based on the force feedback system according to any one of claims 1-8, characterized in that, include: Obtain the target force and the position of the force feedback device; Based on the target force and the position of the force feedback device, calculate the target current of each electromagnet in the electromagnet array; The actual current of the electromagnet is adjusted based on the target current, and the difference between the actual current and the target current is less than a threshold.

10. The force feedback control method according to claim 9, characterized in that, The step of adjusting the actual current of the electromagnet based on the target current, and making the difference between the actual current and the target current less than a threshold, includes: The duty cycle of the corresponding generator is adjusted based on each of the target currents; Obtain the actual current of each electromagnet; The actual current is compared with the target current. If the difference between the actual current and the target current is greater than or equal to a threshold, the duty cycle of the generator is adjusted again. The actual current of each electromagnet is obtained again, and the actual current is compared with the target current again until the difference between the actual current and the target current of each electromagnet is less than a threshold.

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