Gravity balance device and gravity balance error compensation method

Abstract

The invention provides a gravitational equilibrium device and a gravitational equilibrium error compensation method, the gravitational equilibrium device comprises a motor, a volute spiral spring and a variable-diameter cone pulley, and the variable-diameter cone pulley is provided with a spiral groove of which the diameter is gradually changed. By reasonably designing the diameter of the spiral line corresponding to the spiral groove, the gravity balancing device can output constant force all the time, the motor only needs to overcome friction force and tiny spring torque, and the gravity balancing device has a good balancing effect and is longer in service life, longer in maintenance period and simpler and more compact in structure compared with a constant-force spring. Meanwhile, the load error and the error generated by the average torque are compensated to the output torque of the motor, and the error generated by the pitch change and the diameter change of the spiral line is compensated to the theoretical diameter of the spiral line, so that the output of the gravity balancing device is more stable, and the fluctuation of the force is reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of gravity balance, and more specifically, relates to a gravity balance device and a gravity balance error compensation method. Background Art

[0002] In the practical application of mechanical joints, there are some working conditions with large loads. Especially when actively controlling mechanical joints, higher requirements are put forward for the performance of motors such as torque. In some usage scenarios with high requirements for force balance effects, such as force dragging, collaborative robots, etc., there are also high requirements for the force fluctuation output by the gravity balance device.

[0003] The output source of existing gravity balance devices often adopts a constant force spring structure to achieve. One end of the constant force spring structure is connected to the load, and the other end is connected to the driving end to achieve the balance of gravity. However, the above constant force spring structure will cause the gravity balance device to have a large volume, short service life at the same time, and the output force of the spring used in the gravity balance device will fluctuate. When the fluctuation is large, it will even cause the motor to vibrate and the movement cannot be accurately controlled, which limits its usage scenarios to a certain extent. Summary of the Invention

[0004] The purpose of the embodiments of the present invention is to provide a gravity balance device and a gravity balance error compensation method to solve the technical problems of large volume, short life, and large output force fluctuation existing in the prior art.

[0005] To achieve the above purpose, the technical solution adopted by the present invention is: providing a gravity balance device, including a motor, a scroll spring, and a variable diameter sheave. One end of the scroll spring is fixed to the rotating shaft of the motor, and the other end of the scroll spring is fixed to the housing of the motor. The variable diameter sheave is driven by the rotating shaft of the motor to rotate. The outer circumference of the variable diameter sheave has a spiral groove with a gradually changing diameter. The center line of the spiral groove is a spiral line, and the diameter of the spiral line is positively correlated with the rotation angle of the scroll spring.

[0006] In the above solution, the gravity balance device includes a motor, a scroll spring, and a variable diameter sheave, and a spiral groove with a gradually changing diameter is provided on the variable diameter sheave. By reasonably designing the diameter of the spiral line corresponding to the spiral groove, the gravity balance device can always output a constant force. The motor only needs to overcome the friction force and a small spring torque. While having a good balance effect, it has a longer service life than the constant force spring and is more simple and compact in structure.

[0007] Optionally, the diameter of the spiral line is the sum of the theoretical diameter of the spiral line and the error compensation of the spiral line.

[0008] In the above solution, when designing the diameter of the spiral, the theoretical diameter of the spiral can be calculated first, and then, according to the errors caused by other factors, this error can be compensated to the theoretical diameter of the spiral, making the design of the spiral more accurate, the output of the gravity balance device more stable, and reducing the force fluctuation.

[0009] Optionally, the error compensation includes a first error and / or a second error. The first error is the error caused by the pitch change of the spiral, and the second error is the error caused by the diameter change of the spiral.

[0010] In the above solution, by compensating the error of the spiral, the output of the gravity balance device can be made more stable, the force fluctuation can be reduced, and the motor only needs to overcome the friction force and the small spring torque.

[0011] The present invention also provides a gravity balance error compensation method, which is applied to the above gravity balance device and includes the following steps:

[0012] Obtain the first torque error between the actual torque and the average torque of the scroll spring, and compensate the first torque error to the motor output torque.

[0013] In the above solution, by compensating the error generated by the average torque to the output torque of the motor, the output of the gravity balance device can be made more stable, and the force fluctuation can be reduced.

[0014] Optionally, the step of obtaining the first torque error between the average torques of the scroll spring includes:

[0015] Obtain the actual torque of the scroll spring. The actual torque of the scroll spring is the torque in the wound state of the scroll spring or the torque in the relaxed state of the scroll spring;

[0016] Obtain the average torque of the scroll spring. The average torque is the average value of the torques in the wound state and the relaxed state of the scroll spring.

[0017] In the above solution, the actual torque and the average torque of the scroll spring can be obtained respectively through the above steps. The average torque can be calculated, and the actual torque can be obtained through testing. The method for obtaining the first torque error is simple and reliable, conforms to the actual application scenario, and can minimize the error caused by calculating the spiral using the average torque as much as possible.

[0018] Optionally, the gravity balance error compensation method further includes obtaining the gravity error between the actual load and the designed load, calculating the second torque error according to the gravity error, and compensating the second torque error to the motor output torque.

[0019] Optionally, the second torque error is the product of the gravity error and the theoretical diameter of the spiral line.

[0020] In the above solution, the second torque error is the product of the gravity error and the theoretical diameter of the spiral line, that is, the second torque error is ΔM·φ x , φ x is the theoretical diameter of the spiral line. The rotation angle of the scroll spring corresponds one-to-one with the theoretical diameter of the spiral line, and the rotation angle of the scroll spring corresponds one-to-one with the output torque of the motor. Therefore, at different positions (different theoretical diameters) of the spiral line, the corresponding second torque error is compensated to the output torque of the motor through the control algorithm.

[0021] Optionally, the step of obtaining the error compensation of the spiral line includes: obtaining a first error generated due to the change in the pitch of the spiral line.

[0022] In the above solution, during the process of the load gradually moving downward, due to the influence of the pitch of the spiral line, the traction rope gradually deviates from the vertical direction. A part of the force exerted by the traction rope on the load is the horizontal component force, generating a force error and reducing the balancing effect. In order to compensate for this part of the force error, correspondingly, the first error is used as the diameter compensation and compensated to the theoretical diameter φ of the spiral line x , to ensure the balancing effect. When compensating the first error Δφ1 to the theoretical diameter φ of the spiral line x , the diameter of the spiral line is set to φ x +Δφ1.

[0023] Optionally, the gravity balancing device further includes a traction rope, the traction rope is wound around the spiral groove, and one end of the traction rope is fixed to the variable-diameter pulley, and the other end is connected to the load. The gravity balance error compensation method further includes obtaining the error compensation of the spiral line and compensating the error compensation of the spiral line to the theoretical diameter of the spiral line.

[0024] In the above solution, by compensating the errors generated by the change in the pitch and diameter of the spiral line to the theoretical diameter of the spiral line, the output of the gravity balancing device can be made more stable and the force fluctuation can be reduced.

[0025] Optionally, the error compensation includes a first error, and the first error is the error generated by the change in the pitch of the spiral line.

[0026] Optionally, the step of obtaining the first error generated due to the change in the pitch of the spiral line includes:

[0027] Calculating a first distance, where the first distance is the distance between the tangent points of the traction rope and the spiral line when the load is at the starting point and when the load is at the predetermined displacement on the longitudinal section of the variable-diameter pulley;

[0028] Calculate the first included angle according to the first distance, where the first included angle is the included angle between the vertical direction and the traction rope on the longitudinal section of the variable-diameter sheave;

[0029] Calculate the first error according to the first included angle.

[0030] In the above solution, the first error caused by the change in pitch can be calculated by geometric calculation, and the calculation result is relatively accurate.

[0031] Optionally, the error compensation includes a second error, which is the error caused by the change in the diameter of the helical line.

[0032] In the above solution, during the process of the load gradually moving downward, due to the continuous change in the diameter of the helical line, the traction rope gradually deviates from the vertical direction. A part of the force exerted by the traction rope on the load is the horizontal component force, resulting in a force error and reducing the balancing effect. To compensate for this part of the force error, accordingly, the second error is used as the diameter compensation and compensated to the theoretical diameter φ of the helical line x , to ensure the balancing effect. When compensating the second error Δφ2 to the theoretical diameter φ of the helical line x , the diameter of the helical line is set to φ x +Δφ2

[0033] Optionally, the step of obtaining the second error caused by the change in the diameter of the helical line includes:

[0034] Calculate the second distance, where the second distance is the distance between the tangent points of the traction rope and the helical line when the load is at the starting point and when the load is at the predetermined displacement on the cross-section of the variable-diameter sheave;

[0035] Calculate the second included angle according to the second distance, where the second included angle is the included angle between the vertical direction and the traction rope on the cross-section of the variable-diameter sheave;

[0036] Calculate the second error according to the second included angle.

[0037] In the above solution, the second error caused by the change in pitch can be calculated by geometric calculation, and the calculation result is relatively accurate. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0039] Figure 1Cross-sectional view of the gravity balance device provided by the embodiment of the present invention;

[0040] Figure 2 Stereo structure diagram of the gravity balance device provided by the embodiment of the present invention;

[0041] Figure 3 Left view and front view of the rotating shaft provided by the embodiment of the present invention;

[0042] Figure 4 Front view and stereo structure diagram of the variable-diameter pulley provided by the embodiment of the present invention;

[0043] Figure 5 Front view of the gravity balance device provided by the embodiment of the present invention;

[0044] Figure 6 Left view of the variable-diameter pulley provided by the embodiment of the present invention.

[0045] Among them, each reference numeral in the figure:

[0046] 1 - motor; 11 - housing; 111 - left housing; 112 - right housing; 113 - mounting part; 12 - rotating shaft; 13 - stator; 14 - rotor; 2 - scroll spring; 3 - variable-diameter pulley; 32 - spiral groove; 33 - mounting part. Detailed implementation manners

[0047] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0048] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it can be directly on the other element or indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or indirectly connected to the other element.

[0049] It should be understood that the orientation or positional relationship indicated by the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation to the present invention.

[0050] In addition, the terms "first" and "second" are only used for descriptive purposes and should not be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present invention, "a plurality of" means two or more, unless otherwise specifically defined.

[0051] In the actual application of mechanical joints, there are some working conditions with relatively large loads in the gravity direction. Especially when actively controlling the mechanical joint, higher requirements are imposed on the performance of the motor 1 such as torque. In some usage scenarios with high requirements for the force balance effect, such as force dragging and collaborative robots, higher requirements are also imposed on the force fluctuation output by the gravity balance device. The commonly used output sources of existing gravity balance devices include tension springs, constant force springs, scroll springs 2, gas springs, hydraulic balance devices, etc. When a gas spring and a tension spring are connected to the motor 1, rotation needs to be converted into linear movement, so the structural volume is relatively large; the constant force spring has a good balance effect, but its service life is generally short; the scroll spring 2 has a longer service life and greater stiffness compared with the constant force spring, but the spring output force fluctuates greatly; the hydraulic balance device is relatively complex, large in volume, and limited in usage occasions.

[0052] In actual use, the output forces of all springs fluctuate. Especially, the output force of the scroll spring 2 fluctuates relatively more than that of other springs, which poses higher requirements on the motor 1. When the fluctuation is large, it may even cause the motor 1 to vibrate and unable to accurately control the movement, which to a certain extent limits its usage scenarios. To overcome the above technical problems, the present invention proposes a new gravity balance device and a gravity balance error compensation method.

[0053] Now, the gravity balance device provided by the embodiments of the present invention will be described.

[0054] Please refer to Figures 1 to 3 , the gravity balance device includes a motor 1, a scroll spring 2, and a variable diameter pulley 3.

[0055] The motor 1 operates in the powered state and can output rotational motion when working. When this gravity balance device is applied to mechanisms such as vertical joints, the motor 1 can be the mechanism that provides power in the vertical joint. Specifically, the motor 1 has a rotating shaft 12, and the rotating shaft 12 is the power output structure of the motor 1, that is, the rotating shaft 12 outputs rotational motion. The motor 1 further includes a housing 11, a part of the rotating shaft 12 is located inside the housing 11, and one end of the rotating shaft 12 extends outside the housing 11.

[0056] The scroll spring 2 is a spring with one end fixed and a torque acting on the other end; under the action of the torque, the material of the scroll spring 2 produces bending elastic deformation, causing the scroll spring 2 to twist in a plane, and the magnitude of its deformation angle is proportional to the torque. One end of the scroll spring 2 is fixed to the rotating shaft 12 of the motor 1, and the other end of the scroll spring 2 is fixed to the housing 11 of the motor 1. Under the action of the motor 1, the rotation of the rotating shaft 12 drives the scroll spring 2 to wind up or unwind accordingly.

[0057] The variable-diameter pulley 3 is driven to rotate by the rotating shaft 12 of the motor 1, and the variable-diameter pulley 3 can be directly connected or indirectly connected to the rotating shaft 12. The variable-diameter pulley 3 refers to a pulley with a varying diameter of the spiral groove 32 on its outer circumference. Specifically, the outer circumference of the variable-diameter pulley 3 has a spiral groove 32 with a gradually changing diameter, and the center line of the spiral groove 32 is a spiral line, that is to say, the diameter of the spiral line is constantly changing.

[0058] Specifically, when the load is determined, the mass of the load is determined. In order to make the gravity balance device output a constant force (the scroll spring 2 outputs a constant force), the diameter of the spiral line is set in positive correlation with the torque of the scroll spring 2, and the torque of the scroll spring 2 is related to its rotation angle (when the rotating end of the scroll spring 2 rotates one circle, the rotation angle can be recorded as 2π or 360 degrees). The larger the rotation angle of the scroll spring 2, the greater the torque it outputs. After the scroll spring 2 is produced, the relationship between the rotation angle of the scroll spring 2 and the torque it outputs is known, which is related to the material, coil degree, etc. of the scroll spring 2. When the load is moving, when the rotation angle of the scroll spring 2 is constantly increasing, the torque output by the scroll spring 2 is constantly increasing, and the diameter of the spiral line also needs to constantly increase to keep the gravity balance device outputting a constant force. Therefore, the diameter of the spiral line is in positive correlation with the rotation angle of the scroll spring 2. It should be noted that "positive correlation" is not "proportional", that is to say, the diameter of the spiral line is not necessarily set in proportion to the rotation angle of the scroll spring 2, and the ratio of the diameter of the spiral line to the rotation angle of the scroll spring 2 is not necessarily a constant.

[0059] The gravity balance device in the above embodiment includes a motor 1, a scroll spring 2, and a variable-diameter pulley 3, and the variable-diameter pulley 3 is provided with a spiral groove 32 with a gradually changing diameter. By reasonably designing the diameter of the spiral line corresponding to the spiral groove 32, the gravity balance device can always output a constant force. The motor 1 only needs to overcome the friction and a small spring torque, and it has a better balance effect while having a longer service life than a constant force spring and a simpler and more compact structure.

[0060] In some embodiments of the present invention, the spiral groove 32 is for the traction rope to wind around. One end of the traction rope is fixed to the variable-diameter pulley 3, and the other end of the traction rope is connected to the load. That is to say, after the traction rope winds around the variable-diameter pulley 3 along the spiral groove 32, the free end of the traction rope is connected to the load.

[0061] In some embodiments of the present invention, in order to improve the stability of the output of the gravity balance device and reduce the force fluctuation, the error generated by the average torque is compensated to the output torque of the motor 1, thereby improving the stability of the output of the gravity balance device. Further, the load error and the error generated by the average torque can also be compensated together to the output torque of the motor 1. Since the diameter of the spiral line of the variable-diameter pulley 3 is variable, corresponding errors will be generated during the movement of the traction rope. In some embodiments of the present application, in order to improve the accuracy and stability of the output of the gravity balance device, the errors generated by the change in the pitch and diameter of the spiral line can also be compensated to the diameter of the spiral line.

[0062] That is to say, in some embodiments of the present invention, by compensating the load error and the error generated by the average torque to the output torque of the motor 1, and by compensating the errors generated by the change in the pitch and diameter of the spiral line to the diameter of the spiral line, the output of the gravity balance device can be made more stable, the force fluctuation can be reduced, and the motor 1 only needs to overcome the friction force and the tiny spring torque.

[0063] In some embodiments of the present invention, please refer to Figure 4 , the diameter of the spiral line is the sum of the theoretical diameter of the spiral line and the error compensation of the spiral line. When designing the diameter of the spiral line, the theoretical diameter of the spiral line can be calculated first, and then, according to the errors generated by other factors, this error is compensated to the theoretical diameter of the spiral line, so that the design of the spiral line is more accurate, the output of the gravity balance device is more stable, and the force fluctuation is reduced. It should be noted that the theoretical diameter of the spiral line is positively correlated with the rotation angle of the scroll spring 2. After the scroll spring 2 and the load are determined, the theoretical diameter of the spiral line can be calculated. In other embodiments, the diameter of the spiral line can also be directly the theoretical diameter of the spiral line.

[0064] In some embodiments, the relationship between the rotation angle of the scroll spring 2 and the torque it outputs is known, which is related to the material, winding degree, etc. of the scroll spring 2. When the load moves and causes the rotation angle of the scroll spring 2 to continuously increase, the torque output by the scroll spring 2 continuously increases, and the diameter of the spiral line also needs to continuously increase to maintain a constant force output by the gravity balance device. The torque output by the scroll spring 2 is related to the displacement x of the load. Therefore, the theoretical diameter of the spiral line can be represented by φ x and φ x = 2T / M, where T is the average torque of the scroll spring 2, the average torque changes with the change of the rotation angle (the change of the displacement of the load), and M is the gravity of the load.

[0065] In order to calculate the theoretical diameter φ x of the spiral line more conveniently, the displacement x of the load can be used as the independent variable, and φ x as the dependent variable, and a relational expression can be obtained by using polynomial fitting Among them, x is the position of the load, 0 ≤ x ≤ S, S is the stroke of the load, k is the first-order term coefficient of the relationship between the diameter of the variable-diameter pulley 3 and the rotation angle of the scroll spring 2, and φ0 is the starting diameter of the spiral. Determine the stroke S of the load, and generally take S + 20 mm for the length of the spiral; select the starting and ending diameters of the spiral according to the actual structural space. When the gravity balance device is in use, the scroll spring 2 can be pre-tightened by a certain number of turns according to the load weight, so that it can stop at any position of the stroke, and the up and down movement resistance is the same.

[0066] In some embodiments of the present invention, the error compensation of the spiral includes the first error and / or the second error. The first error Δφ1 is the error generated by the pitch change of the spiral, and the second error Δφ2 is the error generated by the diameter change of the spiral. Specifically, the following situations are included: the error compensation of the spiral includes the first error. After error compensation, the diameter of the spiral is set to φ x + Δφ1; the error compensation of the spiral includes the second error. After error compensation, the diameter of the spiral is set to φ x + Δφ2; the error compensation of the spiral includes the first error and the second error. After error compensation, the diameter of the spiral is set to φ x + Δφ1 + Δφ2. By performing error compensation on the spiral, the output of the gravity balance device can be made more stable, the force fluctuation can be reduced, and the motor 1 only needs to overcome the friction force and the small spring torque.

[0067] In some embodiments, please refer to Figure 5 , the load is restricted by a guiding structure such as a slide rail, and the load always moves in a straight line, and its position in the left and right directions always remains unchanged. However, in combination with Figure 5 , during the process of the load gradually moving downward, due to the influence of the pitch of the spiral, the traction rope gradually deviates from the vertical direction, and a part of the force exerted by the traction rope on the load is a horizontal component force, generating a force error and reducing the balancing effect. In order to compensate for this part of the force error, correspondingly, the first error is used as the diameter compensation and compensated to the theoretical diameter φ x of the spiral to ensure the balancing effect. The first error is Δφ1, and the first error Δφ1 can be calculated according to the following steps:

[0068] First, calculate y1,

[0069] y1 = φ x / k·P

[0070] y1 is the distance between the tangent points of the traction rope and the spiral at the starting point of the load and at the load at x on the longitudinal section of the variable-diameter pulley 3, φ x is the theoretical diameter of the spiral, k is the first-order term coefficient of the relationship between the diameter of the variable-diameter pulley 3 and the rotation angle of the scroll spring 2, and P is the pitch of the spiral.

[0071] Then, calculate α based on y1,

[0072]

[0073] α is the angle between the vertical direction and the towing rope on the longitudinal section of the variable-diameter pulley 3; H1 is the distance between the tangent points of the towing rope and the helix at the starting point and the ending point of the load on the longitudinal section of the variable-diameter pulley 3; L is the distance between the initial position of the load and the central axis of the variable-diameter pulley 3, and x is the displacement of the load.

[0074] Finally, calculate the first error Δφ1 based on α,

[0075]

[0076] T is the average torque corresponding to the scroll spring 2 when the load is at the displacement x, and M is the gravity of the load.

[0077] In some embodiments of the present invention, refer to Figure 6 , the load is restricted by guiding structures such as slide rails, and the load always moves in a straight line, and its position in the left-right direction ( Figure 6 corresponding to the up-down direction herein) always remains unchanged. However, in combination with Figure 6 , during the process of the load gradually moving downward, due to the continuously changing diameter of the helix, the towing rope gradually deviates from the vertical direction, and a part of the force exerted by the towing rope on the load is a horizontal component force, generating a force error and reducing the balancing effect. It should be noted that Figure 6 the corresponding direction herein is not the actual direction when the gravity balancing device works, Figure 6 the horizontal direction in x should be the vertical direction when the gravity balancing device works. To avoid confusion, the following descriptions are all in the actual direction when the gravity balancing device works. To compensate for this part of the force error, accordingly, the second error is used as the diameter compensation and compensated to the theoretical diameter φ

[0078] First, calculate y2,

[0079] y2 = φ x / k·P·tanΦ

[0080] y2 is the distance between the tangent points of the towing rope and the helix at the starting point of the load and at x on the cross-section of the variable-diameter pulley 3; φ x is the theoretical diameter of the helix, k is the first-order term coefficient of the relationship between the diameter of the variable-diameter pulley 3 and the rotation angle of the scroll spring 2, P is the pitch of the helix, and Φ is the cone angle of the variable-diameter pulley 3.

[0081] Then, calculate β according to y2.

[0082]

[0083] β is the angle between the vertical direction and the towing rope on the cross-section of the variable-diameter sheave 3; H2 is the distance between the tangent points of the towing rope and the spiral line when the load is at the starting point and the ending point on the cross-section of the variable-diameter sheave 3; L is the distance between the initial position of the load and the central axis of the variable-diameter sheave 3, and x is the displacement of the load.

[0084] Finally, calculate the second error Δφ2 according to β.

[0085]

[0086] T is the average torque corresponding to the scroll spring 2 when the load is at the displacement x, and M is the gravity of the load.

[0087] In some embodiments of the present invention, please refer to Figure 1 and Figure 2 , the housing 11 of the motor 1 includes a left housing 111 and a right housing 112. The left housing 111 and the right housing 112 are fixedly connected, and both ends of the rotating shaft 12 are respectively supported on the left housing 111 and the right housing 112. By dividing the housing 11 into the left housing 111 and the right housing 112, it is easier to process and install the housing 11 of the motor 1.

[0088] In some embodiments of the present invention, please refer to Figure 3 , both ends of the scroll spring 2 are respectively connected to the rotating shaft 12 and the housing 11 of the motor 1, and both connection parts are mounting parts 113. The mounting part 113 on the rotating shaft 12 is arranged at a position where the rotating shaft 12 extends along its axial direction, and one end of the scroll spring 2 can be inserted into the rotating shaft 12 along the radial direction of the rotating shaft 12. The mounting part 113 on the housing 11 can be located on the inner wall of the housing 11.

[0089] In some embodiments of the present invention, please refer to Figure 1 , the motor 1 further includes a stator 13 and a rotor 14. The stator 13 is fixed to the inner wall of the housing 11, the rotor 14 is arranged inside the stator 13, the rotating shaft 12 is fixedly connected to the rotor 14 and passes through the rotor 14, and the scroll spring 2 is arranged between the outer wall of the rotating shaft 12 and the inner wall of the housing 11.

[0090] In some embodiments of the present invention, please refer to Figure 4 , a mounting part 33 is arranged at the starting position of the spiral groove 32, and the mounting part 33 is used to fix one end of the towing rope.

[0091] The present invention also provides a gravity balance error compensation method, which is applied to the gravity balance device in any of the above embodiments. The gravity balance error compensation method includes the following steps:

[0092] S10: Obtain the first torque error between the actual torque and the average torque of the scroll spring 2, and compensate the first torque error to the output torque of the motor 1.

[0093] Step S10 is used to compensate the first torque error between the actual torque and the average torque of the scroll spring 2 to the output torque of the motor 1. The relationship between the torque of the scroll spring 2 and the rotation angle of the scroll spring 2 is not completely linear, the actual torque fluctuates greatly, and the average torque and the actual torque are not the same. When calculating the theoretical diameter φ of the helix x the average torque of the scroll spring is used. Therefore, there is a first torque error between the average torque and the tightened and relaxed states of the scroll spring. The first torque error will cause a sudden change in the load of the motor 1 during actual use, resulting in vibration of the motor 1 and even the situation of incomplete movement. By compensating the first torque error to the output torque of the motor 1, the sudden change in the load of the motor 1 can be reduced and the vibration of the motor 1 can be reduced.

[0094] In the above embodiment, by compensating the error generated by the average torque to the output torque of the motor 1, the output of the gravity balance device can be made more stable and the force fluctuation can be reduced.

[0095] In some embodiments of the present invention, in step S10, the step of obtaining the first torque error between the actual torque and the average torque of the scroll spring 2 includes:

[0096] S11: Obtain the actual torque of the scroll spring 2. The actual torque of the scroll spring 2 is the torque in the tightened state of the scroll spring 2 or the torque in the relaxed state of the scroll spring 2;

[0097] S12: Obtain the average torque of the scroll spring 2. The average torque is the average value of the torques in the tightened state and the relaxed state of the scroll spring 2.

[0098] Through the above steps, the actual torque and the average torque of the scroll spring 2 can be obtained respectively. The average torque can be calculated, and the actual torque can be obtained through testing. The method for obtaining the first torque error is simple and reliable, conforms to the actual application scenario, and can minimize the error caused by using the average torque to calculate the helix.

[0099] In some embodiments, in step S11, the actual torque of the scroll spring 2 is the actual output torque of the scroll spring 2 when the gravity balance device is connected with a load. Affected by factors such as friction and machining errors, there may be a certain error between the actual torque and the theoretical average torque. The actual output torque of the scroll spring 2 can be obtained by testing methods. The actual output torque of the scroll spring 2 can be the torque of the scroll spring 2 in the wound state or the torque of the scroll spring 2 in the relaxed state. In fact, the torque of the scroll spring 2 in the wound state and the torque in the relaxed state differ very little, so either one of the torques can be used.

[0100] It should be noted that the actual torque of the scroll spring 2 is not a fixed value. The actual torque of the scroll spring 2 increases as the rotation angle of the scroll spring 2 increases. That is to say, the actual torque of the scroll spring 2 is related to the displacement of the load. When testing the actual torque of the scroll spring 2, the actual torque of the scroll spring 2 can be tested at multiple displacements of the load, and the functional relationship between the actual torque of the scroll spring 2 and the displacement of the load can be obtained by fitting.

[0101] In some embodiments, in step S12, the average torque is the average value of the torques of the wound state and the relaxed state of the scroll spring 2. After the scroll spring 2 is produced, the average torque is a determined value. The torque of the scroll spring 2 in the wound state and the torque of the scroll spring 2 in the relaxed state can be obtained by looking up the characteristic curve of the scroll spring 2, etc., so that the average torque of the scroll spring 2 can be obtained. The average torque of the scroll spring 2 can also be obtained by testing methods.

[0102] In some embodiments, step S12 includes:

[0103] S121: Select multiple scroll springs 2 and test their characteristic curves;

[0104] S122: Obtain the pre-average torque according to the characteristic curves of the respective scroll springs 2;

[0105] S123: Calculate the pre-torque error between the test torque and the pre-average torque of the scroll spring 2. The scroll spring 2 with a pre-torque error less than a predetermined value is a qualified spring;

[0106] S124: Obtain the average torque according to the characteristic curves of the respective qualified springs.

[0107] In step S12, the average torque of the scroll spring 2 is obtained through testing, making the numerical value of the average torque of the scroll spring 2 more accurate. During mass production, the characteristic curves of the scroll springs 2 can be sampled and tested proportionally. The average torque of multiple scroll springs 2 is the pre-average torque, which is used as the design basis for the spiral. Then, the pre-torque error of each scroll spring 2 caused by the pre-average torque is calculated, and the scroll springs 2 with larger errors are excluded. The average torque of the qualified scroll springs 2 is recalculated, and the spiral is designed based on this average torque, which can meet the usage requirements of a large number of scroll springs 2.

[0108] In step S121, a certain number of scroll springs 2 are sampled proportionally from the scroll springs 2 produced in large quantities. Through testing, their characteristic curves can be obtained. The characteristic curve is a curve with the rotation angle of the scroll spring 2 as the abscissa and the torque of the scroll spring 2 as the ordinate.

[0109] In step S122, each scroll spring 2 corresponds to a characteristic curve. By averaging the respective characteristic curves, the pre-average torque can be obtained. Specifically, the torques corresponding to the same rotation angle of each scroll spring 2 can be averaged to obtain the pre-average torque. Since the specific value of the pre-average torque is related to the corresponding rotation angle, the pre-average torque can also be understood as a pre-characteristic curve.

[0110] In step S123, the test torque of the scroll spring 2 can be understood as the characteristic curve obtained by testing the scroll spring 2. The difference between this characteristic curve and the pre-characteristic curve is the pre-torque error. The scroll spring 2 with a pre-torque error less than a predetermined value is a qualified spring. At different rotation angle values, the pre-torque error is different. It can be set that the scroll spring 2 with a pre-torque error less than the predetermined value at each rotation angle is a qualified spring. Of course, it can also be set that the scroll spring 2 with a pre-torque error less than the predetermined value at some rotation angles is a qualified spring.

[0111] In step S124, the average torque is obtained based on the characteristic curves of each qualified spring. The characteristic curve of the qualified spring is the scroll spring 2 obtained by testing, which is equivalent to recalculating the average torque of the qualified scroll springs 2 after excluding the scroll springs 2 with larger errors.

[0112] It should be noted that the average torque of the scroll spring 2 is not a fixed value. The average torque of the scroll spring 2 increases as the rotation angle of the scroll spring 2 increases. That is to say, the average torque of the scroll spring 2 is related to the displacement of the load. There is a corresponding functional relationship between the average torque of the scroll spring 2 and the displacement of the load.

[0113] In step S10, the first torque error can be obtained through any of the above embodiments, and then the first torque error is compensated to the output torque of the motor 1. The output torque of the motor 1 is a predetermined output torque, referred to as the predetermined output torque. Adding the first torque error to the predetermined output torque can obtain the actual output torque. Inputting this actual output torque into the control system of the motor 1 can achieve compensating the first torque error to the output torque of the motor 1. There are corresponding functional relationships between the actual torque and the average torque of the scroll spring 2 and the displacement of the load. Therefore, there is also a corresponding functional relationship between the first torque error and the displacement of the load. When the load is at different displacements, the corresponding first torque error is compensated to the output torque of the motor 1.

[0114] In some embodiments of the present invention, the gravity balance error compensation method further includes S20: obtaining the gravity error between the actual load and the designed load, calculating the second torque error according to the gravity error, and compensating the second torque error to the output torque of the motor 1.

[0115] Step 20 is used to convert the gravity error between the actual load and the designed load into the second torque error and compensate the second torque error to the output torque of the motor 1. The scroll spring 2 of the gravity balance device is pre-tightened according to the theoretical load weight. During actual use, there may be a gravity error between the actual load and the theoretical load, and this gravity error will reduce the balancing effect. By compensating the second torque error to the output torque of the motor 1, the balancing effect can be improved.

[0116] In the above embodiments, by compensating the error generated by the load error to the output torque of the motor 1, the output of this gravity balance device can be made more stable and the force fluctuation can be reduced.

[0117] In some embodiments of the present invention, in step S20, the gravity error between the actual load and the designed load is obtained, the second torque error is calculated according to the gravity error, and the second torque error is compensated to the output torque of the motor 1. Due to processing errors and other reasons, the gravity of the actual load may have a difference from the gravity of the designed load. When the gravity of the load changes, the output torque of the motor 1 needs to be adjusted accordingly to better maintain gravity balance.

[0118] In some embodiments, the gravity of the actual load is known, the gravity of the designed load is known, and the gravity error ΔM between the actual load and the designed load can be obtained through simple calculation.

[0119] In some embodiments, the second torque error is the product of the gravity error and the theoretical diameter of the spiral, that is, the second torque error is ΔM·φ x , φ xis the theoretical diameter of the spiral. The rotation angle of the scroll spring 2 corresponds one-to-one with the theoretical diameter of the spiral, and the rotation angle of the scroll spring 2 corresponds one-to-one with the output torque of the motor 1. Therefore, at different positions of the spiral (different theoretical diameters), the corresponding second torque error is compensated to the output torque of the motor 1 through a control algorithm.

[0120] Among them, in order to calculate the theoretical diameter φ of the spiral more conveniently x , the displacement x of the load can be used as the independent variable, and φ x as the dependent variable, and a relational expression can be obtained by using polynomial fitting where x is the position of the load, 0 ≤ x ≤ S, S is the stroke of the load, k is the first-order term coefficient of the relational expression between the diameter of the variable-diameter pulley 3 and the rotation angle of the scroll spring 2, and φ0 is the starting diameter of the spiral.

[0121] In some embodiments of the present invention, the gravity balance device further includes a traction rope, the traction rope is wound around the spiral groove 32, and one end of the traction rope is fixed to the variable-diameter pulley (3), and the other end is connected to the load. The gravity balance error compensation method further includes S30: obtaining the error compensation of the spiral and compensating the error compensation of the spiral to the theoretical diameter of the spiral.

[0122] It should be noted that S10, S20, and S30 can all perform error compensation on the gravity balance device respectively to make its balance effect better. The implementation order of S10, S20, and S30 is not limited here. S10, S20, and S30 are parallel to each other, and can be implemented simultaneously or in any order.

[0123] Step 30 is used to compensate the error compensation of the spiral to the theoretical diameter of the spiral. The load is restricted by guiding structures such as slide rails, and the load always moves in a straight line, and its position in the left-right direction always remains unchanged. However, in combination with Figure 5 and Figure 6 , during the process of the load gradually moving downward, due to the influence of the change of the spiral pitch and the spiral diameter, the traction rope gradually deviates from the vertical direction, and a part of the force exerted by the traction rope on the load is the horizontal component force, generating a force error and reducing the balance effect.

[0124] In the above embodiments, by compensating the errors caused by the change of the spiral pitch and the diameter to the theoretical diameter of the spiral, the output of the gravity balance device can be made more stable and the force fluctuation can be reduced.

[0125] In some embodiments of the present invention, the error compensation includes a first error, and the first error is the error generated by the pitch change of the spiral. Specifically, step S30 includes step S31, and step S31 is to obtain the first error generated by the pitch change of the spiral. The load is restricted by a guiding structure such as a slide rail, and the load always moves in a straight line, and its position in the left-right direction always remains unchanged. However, in combination with Figure 5 , during the process of the load gradually moving downward, due to the influence of the spiral pitch, the traction rope gradually deviates from the vertical direction, and a part of the force exerted by the traction rope on the load is a horizontal component force, generating a force error and reducing the balancing effect. In order to compensate for this part of the force error, correspondingly, the first error is used as the diameter compensation and compensated to the theoretical diameter φ of the spiral x , to ensure the balancing effect. When compensating the first error Δφ1 to the theoretical diameter φ of the spiral x , the diameter of the spiral is set to φ x + Δφ1.

[0126] In some embodiments, step S31 includes:

[0127] S311: Calculate a first distance, where the first distance is the distance between the tangent points of the traction rope and the spiral at the starting point of the load and at the predetermined displacement on the longitudinal section of the variable-diameter pulley 3;

[0128] S312: Calculate a first angle according to the first distance, where the first angle is the angle between the vertical direction and the traction rope on the longitudinal section of the variable-diameter pulley 3;

[0129] S313: Calculate the first error according to the first angle.

[0130] Through the above steps, the first error generated by the pitch change can be calculated by means of geometric calculation, and the calculation result is relatively accurate.

[0131] In step S311, according to the theoretical diameter φ of the spiral x the first distance is calculated, and the first distance can be positively correlated with φ x .

[0132] In some embodiments, the first distance is set as y1, y1 = φ x / k·P, where k is the first-order term coefficient of the relationship between the diameter of the variable-diameter pulley 3 and the rotation angle of the scroll spring 2, and P is the pitch of the spiral.

[0133] In step S312, the first angle is calculated according to the first distance, and specifically, the first angle can be calculated through trigonometric function relationships.

[0134] In some embodiments, the first angle is set as α, H1 is the distance between the tangent points of the traction rope and the spiral line at the starting point and the ending point of the load on the longitudinal section of the variable-diameter sheave 3; L is the distance between the initial position of the load and the central axis of the variable-diameter sheave 3, and x is the displacement of the load.

[0135] In step S313, the first error is calculated according to the first included angle. The first error is set as Δφ1. T is the average torque corresponding to the scroll spring 2 when the load is at the displacement x, and M is the gravity of the load.

[0136] In some embodiments of the present invention, the error compensation includes a second error, and the second error is the error caused by the change in the diameter of the spiral line. Specifically, step S30 includes step S32, and step S32 is to obtain the second error caused by the change in the diameter of the spiral line. The load is restricted by a guiding structure such as a slide rail, and the load always moves in a straight line, and its position in the left-right direction ( Figure 6 corresponding to the up-down direction in this case) always remains unchanged. However, in combination with Figure 6 , during the process of the load gradually moving downward, due to the continuous change in the diameter of the spiral line, the traction rope gradually deviates from the vertical direction, and a part of the force exerted by the traction rope on the load is a horizontal component force, generating a force error and reducing the balancing effect. To compensate for this part of the force error, correspondingly, the second error is used as the diameter compensation and compensated to the theoretical diameter φ x of the spiral line to ensure the balancing effect. When compensating the second error Δφ2 to the theoretical diameter φ x of the spiral line, the diameter of the spiral line is set as φ x +Δφ2.

[0137] In some embodiments, step S32 includes:

[0138] S321: Calculate the second distance, which is the distance between the tangent points of the traction rope and the spiral line at the starting point and the pre-displacement of the load on the cross-section of the variable-diameter sheave 3.

[0139] S322: Calculate the second included angle according to the second distance, and the second included angle is the included angle between the vertical direction and the traction rope on the cross-section of the variable-diameter sheave 3;

[0140] S323: Calculate the second error according to the second included angle.

[0141] Through the above steps, the second error caused by the change in the pitch can be calculated by geometric calculation, and the calculation result is relatively accurate.

[0142] In step S321, the second distance is calculated according to the theoretical diameter φ x of the spiral line, and the second distance can be positively correlated with φ x .

[0143] In some embodiments, the second distance is set as y2, and y2 = φ x / k·P·tanΦ, where k is the first-order term coefficient of the relationship between the diameter of the variable-diameter pulley 3 and the rotation angle of the scroll spring 2, P is the pitch of the helix, and Φ is the cone angle of the variable-diameter pulley 3.

[0144] In step S322, the second included angle is calculated according to the second distance, and specifically, the second included angle can be calculated through trigonometric relations.

[0145] In some embodiments, the second included angle is set as β, H2 is the distance between the tangent points of the traction rope and the helix at the starting point and the ending point of the load on the cross-section of the variable-diameter pulley 3; L is the distance between the initial position of the load and the central axis of the variable-diameter pulley 3, and x is the displacement of the load.

[0146] In step S323, the second error is calculated according to the second included angle. The second error is set as Δφ2, T is the average torque corresponding to the scroll spring 2 when the load is at the displacement x, and M is the gravity of the load.

[0147] In some embodiments of the present invention, the error includes the first error and the second error, that is, step S30 includes step S31 and step S32 at the same time, and when compensating the first error Δφ1 and the second error Δφ2 to the theoretical diameter φ of the helix at the same time x the diameter of the helix is set as φ x +Δφ1+Δφ2.

[0148] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A gravity balance device, characterized in that, It includes a motor (1), a volute spring (2) and a stepped pulley (3). One end of the volute spring (2) is fixed to the rotating shaft (12) of the motor (1), and the other end of the volute spring (2) is fixed to the housing (11) of the motor (1). The stepped pulley (3) is driven by the rotating shaft (12) of the motor (1) to rotate. The outer circumference of the stepped pulley (3) has a spiral groove (32) with a gradually changing diameter. The center line of the spiral groove (32) is a spiral line, and the diameter of the spiral line is positively correlated with the rotation angle of the volute spring (2).

2. A gravity balance error compensation method applied to the gravity balance device according to claim 1, characterized in that, Comprising: Obtain a first torque error between the actual torque and the average torque of the volute spring (2), and compensate the first torque error to the motor output torque.

3. The gravity balance error compensation method according to claim 2, characterized in that, The step of obtaining the first torque error between the average torques of the volute spring (2) includes:[[]] Obtain the actual torque of the volute spring (2). The actual torque of the volute spring (2) is the torque in the wound state of the volute spring (2) or the torque in the relaxed state of the volute spring (2). Obtain the average torque of the volute spring (2). The average torque is the average value of the torques in the wound state and the relaxed state of the volute spring (2).

4. The gravity balance error compensation method according to claim 2, characterized in that, Further comprising: Obtain a gravity error between the actual load and the designed load, calculate a second torque error according to the gravity error, and compensate the second torque error to the motor output torque.

5. The gravity balance error compensation method according to claim 4, characterized in that, The second torque error is the product of the gravity error and the theoretical diameter of the spiral line.

6. The gravity balance error compensation method according to claim 2, characterized in that, The gravity balance device further includes a towing rope. The towing rope is wound around the spiral groove (32), and one end of the towing rope is fixed to the stepped pulley (3), and the other end is connected to the load. The gravity balance error compensation method further includes:[[]] Obtain the error compensation of the spiral line, and compensate the error compensation of the spiral line to the theoretical diameter of the spiral line.

7. The gravity balance error compensation method according to claim 6, characterized in that, The error compensation includes a first error, and the first error is the error generated by the pitch change of the spiral line.

8. The gravity balance error compensation method according to claim 7, characterized in that, The step of obtaining the first error generated by the pitch change of the spiral line includes:[[]] Calculate a first distance, which is the distance between the tangent points of the towing rope and the spiral line when the load is at the starting point and when the load is at the predetermined displacement on the longitudinal section of the stepped pulley (3). Calculate a first angle according to the first distance. The first angle is the angle between the vertical direction and the towing rope on the longitudinal section of the stepped pulley (3). Calculate the first error according to the first angle.

9. The gravity balance error compensation method according to claim 6, characterized in that, The error compensation includes a second error, and the second error is the error generated by the diameter change of the spiral line.

10. The gravity balance error compensation method according to claim 9, characterized in that, The step of obtaining the second error generated by the diameter change of the spiral line includes:[[]] Calculate a second distance, which is the distance between the tangent points of the towing rope and the spiral line when the load is at the starting point and when the load is at the predetermined displacement on the cross section of the stepped pulley (3). Calculate a second angle according to the second distance. The second angle is the angle between the vertical direction and the towing rope on the cross section of the stepped pulley (3). Calculate the second error according to the second included angle.

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