Positioning arm

Abstract

A positioning arm comprises: a link assembly having a translation link that can translate along a virtual axis passing through a remote center of motion (RCM) at a specified distance from a point, and can rotate in at least two directions around the point; and a gravity torque compensation portion that provides a compensation torque, the direction of which is opposite to the direction of the gravity torque caused by the link assembly's own weight acting on the point.

Description

Technical Field

[0001] Example embodiments relate to a positioning arm. Background Art

[0002] Robots are used in many fields such as medicine and industry. For example, in the medical field, as part of a surgical robot system, a support device including a positioning arm is used to freely and stably position surgical instruments and robot arms.

[0003] Positioning arms with rotational freedom are usually used and are widely used in surgical robots such as laparoscopic surgical robots and the Da Vinci system. The weight of the positioning arm itself or the weight of the instrument loaded on the positioning arm will act on the joints of the positioning arm, thereby generating gravitational torque. The gravitational torque may change the posture of the positioning arm, so a constant force needs to be continuously applied to keep the posture of the positioning arm unchanged. For example, the user can provide the force to support the positioning arm, or an actuator such as a motor can be used to provide continuous torque, or a brake can be used for fixing.

[0004] However, due to the weight of the positioning arm, it is very difficult for the user to perform surgery while continuously providing force, and the weight of the positioning arm that can be borne is limited. In addition, even if an actuator such as a motor is used, there is still the problem of applying an excessive load, and solving this problem often leads to increased prices, larger volume, and low efficiency relative to volume. When using a brake for fixing, the brake needs to be released and tightened, which reduces the convenience of use, and when the brake is released to adjust the position of the positioning arm, the weight of the positioning arm still needs to be borne manually. Therefore, a gravity compensation device is needed to compensate for the weight of the positioning arm itself.

[0005] The contents of the above background technology are the contents mastered or learned by the inventor in the process of developing the present invention, and should not be understood as necessarily being the general known technology disclosed before applying for the present invention. Summary of the invention

[0006] Technical issues

[0007] This aspect provides a positioning arm that employs a gravity compensation mechanism for three-degree-of-freedom motion.

[0008] Technical Solution

[0009] According to one embodiment, a positioning arm includes: a connecting rod assembly, which has a translation connecting rod that can translate along a virtual axis passing through a remote center of motion (RCM) at a specified distance from a point, and rotate in at least two directions around the point; and a gravity torque compensation part, which provides a compensation torque, the direction of which is opposite to the direction of the gravity torque caused by the own weight of the connecting rod assembly acting on the point.

[0010] The link assembly can roll and pitch, and the translation link is not affected by the roll and pitch angles and can translate along a virtual axis passing through the remote motion center.

[0011] The connecting rod assembly also includes: a gear box, which can roll and rotate relative to the bottom; a pitch link, which can pitch and rotate relative to the gear box; a parallel link, which can move in a posture parallel to the length direction of the pitch link; and a connecting rod connecting the pitch link and the parallel link, and the translation link can translate along a guide located on the parallel link.

[0012] The positioning arm also includes: a central bevel gear fixed to the bottom; a pair of rotating bevel gears respectively meshed on both sides of the central bevel gear and rotatable relative to the gear box; and a pair of rotating bodies respectively fixed to the pair of rotating bevel gears and rotatable relative to the gear box together with the pair of bevel gears.

[0013] A connecting shaft portion is formed between the pair of rotating bevel gears and the pair of rotating bodies corresponding thereto, respectively, and the connecting rod assembly is arranged on the connecting shaft portion in a manner that it can rotate in one direction.

[0014] The pair of rotating bevel gears will not move relative to each other when the connecting rod assembly rotates in pitch, and will rotate in opposite directions relative to the same axis when the connecting rod assembly rotates in roll.

[0015] The gravity torque compensating portion includes a pair of elastic bodies whose lengths are changed according to a rolling rotation or a pitching rotation of the link assembly, thereby providing an elastic force for generating the compensation torque.

[0016] The gravity torque compensation part also includes: a support platform, which is located on one side of the pair of elastic bodies; a pair of sliders, which are located on the other side of the pair of elastic bodies and can slide relative to the pitch link; a pair of compensation steel wires, one side of which is respectively fixed to the pair of rotating bodies, and the other side is respectively fixed to the pair of sliders.

[0017] The positioning arm further includes a gravity torque adjustment portion that reduces a difference between the gravity torque generated along a translation distance of the translation link and the compensation torque.

[0018] The support platform includes a support portion, which is arranged on the side of the path through which the pair of compensation steel wires pass, and plays the function of receiving the compensation torque from the pair of compensation steel wires. When the translation link translates toward the remote motion center, the gravity torque adjustment portion lowers the support platform, thereby reducing the lever arm length of the compensation torque. When the translation link translates in a direction away from the remote motion center, the support platform is raised, thereby increasing the lever arm length of the compensation torque.

[0019] The support platform is arranged to be slidable relative to the pitch link, and the gravity torque adjustment unit includes an adjustment steel wire, which interconnects the translation link and the support platform, thereby sliding the support platform when the translation link translates.

[0020] The gravity torque adjustment unit further includes a speed change means for increasing or decreasing a sliding distance of the support platform relative to the pitch link in proportion to a translation distance of the translation link relative to the parallel link.

[0021] The adjustment steel wire includes a first adjustment steel wire and a second adjustment steel wire respectively connected to one side and the other side of the speed changing means, and the speed changing means includes: a first reel for winding the first adjustment steel wire; a second reel for winding the second adjustment steel wire; and a reducer that enables the second reel to rotate relative to the first reel at a set rotation ratio.

[0022] The positioning arm further includes a gravity torque adjustment portion that reduces a difference between the gravity torque generated along a translation distance of the translation link and the compensation torque.

[0023] According to one embodiment, the positioning arm includes: a connecting rod assembly, which can roll and pitch, and has a translation connecting rod that can translate along a virtual axis passing through a remote center of motion (RCM) at a specified distance from a point; and a plurality of bevel gears, which do not move relative to each other when the connecting rod assembly pitches, and mesh and rotate when the connecting rod assembly rolls; a rotating body, which is connected to one or more of the plurality of bevel gears and rotates together with the bevel gears; and a gravity torque compensation part, which is connected to the rotating body and deforms an elastic body as the connecting rod assembly rolls and pitches, thereby providing a compensation torque, and the direction of the compensation torque is opposite to the gravity torque due to the connecting rod assembly's own weight.

[0024] The positioning arm further includes a gravity torque adjustment portion, which increases or decreases the length of the force arm of the compensation torque according to the translation of the translation link, thereby reducing the difference between the gravity torque and the compensation torque.

[0025] Advantageous Effects of the Invention

[0026] According to an embodiment, the positioning arm can be operated with very little force by utilizing a gravity compensation mechanism. In other words, the input torque to be applied to the driving source can be reduced by the gravity compensation mechanism, so a relatively small and light actuator can be used for driving, reducing the energy consumption simply for compensating for gravity and improving energy efficiency.

[0027] Furthermore, even if an emergency power outage occurs during the use of the positioning arm, the positioning arm will not sink due to gravity, which can particularly improve safety in the field of surgical robots.

[0028] According to an embodiment, the positioning arm has a gravity compensation mechanism, which can compensate for the change in the center of gravity due to the three-degree-of-freedom motion of the end of the positioning arm, namely, roll, pitch, and translation, and can stably maintain various postures in a hemispheric work space without being affected by gravity. Therefore, it can be widely used in surgical robots such as minimally invasive surgery with fulcrum motion. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 is a perspective view of a positioning arm according to an embodiment.

[0030] Figure 2 is a side view conceptually showing a positioning arm according to an embodiment.

[0031] Figure 3 2 is a diagram showing the pitch rotation of a positioning arm and the translation of a translation link according to an embodiment.

[0032] Figure 4 The diagram is a plan view schematically showing a portion of a positioning arm according to an embodiment of the present invention in a state where the positioning arm is pitched and rotated 90 degrees forward.

[0033] Figure 5 FIG. 2 is a diagram showing the pitch rotation of a positioning arm according to an embodiment.

[0034] Figures 6 to 8 FIG. 2 is a diagram showing the rolling rotation of a positioning arm according to an embodiment.

[0035] Fig. 9 and Fig.10 FIG. 1 is a diagram showing the operation of a gravity torque adjustment unit of a translation link during translation according to an embodiment.

[0036] Fig.11 is a conceptual diagram of a positioning arm according to an embodiment.

[0037] Fig.12a2 is a diagram showing a gravity torque adjustment unit according to an embodiment.

[0038] Figure 12b It is shown Fig.12a An enlarged view of part A of FIG.

[0039] Fig.13 2 is a diagram showing a gravity torque adjustment unit according to an embodiment. DETAILED DESCRIPTION

[0040] The embodiments are described in detail below with reference to the example drawings. When assigning reference numerals to the constituent elements in the drawings, the same reference numerals are used as much as possible even if the same constituent elements are represented in different drawings. In the process of describing the embodiments, when it is determined that the specific description of the related known technology will unnecessarily confuse the embodiments, its detailed description is omitted.

[0041] Furthermore, when describing the constituent elements of the embodiments, terms such as first, second, A, B, (a), (b) and the like may be used. These terms are only used to distinguish a constituent element from other constituent elements, and are not used to limit the nature or order of the corresponding constituent elements. For example, a first constituent element may be referred to as a second constituent element, and similarly, a second constituent element may also be referred to as a first constituent element. In addition, it should be understood that when the specification states that a constituent element is "connected", "combined" or "contacting" another constituent element, a third constituent element may be "connected", "combined" or "contacting" between the first constituent element and the second constituent element, although the first constituent element can be directly connected, combined or contacting the second constituent element.

[0042] When a component has a common function with a component of a certain embodiment, the same name is used to describe the component in other embodiments. If no counterexample is mentioned, the description of a certain embodiment can be applied to other embodiments, and the detailed description of the repeated content is omitted.

[0043] Figure 1 is a perspective view of a positioning arm according to an embodiment; Figure 2 is a side view conceptually showing a positioning arm according to an embodiment; Figure 3 is a diagram showing the pitch rotation of the positioning arm and the translation of the translation link according to an embodiment; Figure 4 The diagram is a plan view schematically showing a portion of a positioning arm according to an embodiment of the present invention in a state where the positioning arm is pitched and rotated 90 degrees forward.

[0044] Reference Figures 1 to 4 According to an embodiment, the end 114 of the positioning arm 1 can achieve at least three degrees of freedom relative to the base B, specifically roll rotation, pitch rotation and translation. Figures 1 to 4The coordinate system (x0, y0, z0) shown is a global coordinate system with the origin being the "point" where the roll rotation axis (axis 1) and the pitch rotation axis (axis 2) intersect, and the x0 axis is set as the gravity direction.

[0045] The positioning arm 1 has a means for providing a compensating torque opposite to the gravity torque acting on a point, thereby reducing the power required for maintaining the posture of the positioning arm 1. The positioning arm 1 may include a link assembly 11, a central bevel gear 13, a rotating bevel gear 14, a rotating body 15, a connecting shaft portion 16, a gravity torque compensating portion 17, and a gravity torque adjusting portion 18.

[0046] The link assembly 11 has a translation link 114 that translates along a virtual axis passing through a remote center of motion (RCM) at a specified distance from a point, and can rotate in at least two directions with a point as the center. For example, the link assembly 11 can roll and pitch, and the translation link 114 can translate along an axis passing through the remote center of motion (RCM) without being affected by the roll rotation angle and the pitch rotation angle. The link assembly 11 may include a gear box 111, a pitch link 112, a translation link 114, a parallel link 115, and a connecting rod 116.

[0047] The gear box 111 can roll and rotate relative to the bottom B. For example, the gear box 111 is rotatably connected to a connecting shaft portion (not given a reference numeral) that connects the central bevel gear 13 and the bottom B. The gear box 111 has a structure through which the rotating shafts of the plurality of bevel gears 13 and 14 pass, and supports the meshing of the rotating bevel gear 14 with the central bevel gear 13.

[0048] The pitch link 112 can pitch and rotate relative to the gear box 111. For example, the pitch link 112 can be rotatably connected to the connecting shaft 16 that connects the rotating bevel gear 14 and the rotating body 15. For example, the pitch link 112 can include a first pitch link 1121 and a second pitch link 1122 that are arranged parallel to each other.

[0049] The translation link 114 can rotate in roll and pitch relative to the base B, and can translate along a virtual axis passing through the remote center of motion (RCM). For example, the translation link 114 can translate along a guide 1152 located on the parallel link 115. Figure 1 The translation link 114 is shown briefly in FIG. Figure 2 and Figure 3 etc., various equipment of the remote center of motion (RCM) such as various surgical tools (E) that need to be embodied are set on the translation link 114 etc.

[0050] The parallel link 115 can move in a posture parallel to the length direction of the pitch link 112. The parallel link 115 may include a crossbar 1151 connected to the connecting rod 116; and a guide member 1152 disposed in a vertical direction of the crossbar 1151 for guiding the translation link 114.

[0051] The connecting rod 116 may connect the pitch link 112 and the parallel link 115. The connecting rod 116 may be arranged to be parallel to a virtual line connecting the rotation axis of the first pitch link 1121 and the rotation axis of the second pitch link 1122. For example, the connecting rod 116 may include a first connecting rod 1161 and a second connecting rod 1162 that are parallel to each other. The pitch link 112 may be arranged to be parallel to a virtual line connecting the rotation axis of the first connecting rod 1161 and the rotation axis of the second connecting rod 1162.

[0052] Based on the above structure of the link assembly 11, the pitch link 112, the parallel link 115 and the connecting rod 116 can realize the movement of a parallelogram-like four-bar linkage. Figure 2 and Figure 3 As shown, the translation link 114 can achieve translation along a virtual axis passing through the remote center of motion (RCM) without being affected by the pitch rotation angle of the positioning arm 1. Moreover, when the roll rotation axis (axis 1) and the pitch rotation axis (axis 2) intersect at the same point, the translation link 114 can still achieve translation along the same virtual axis passing through the remote center of motion (RCM) without being affected by the roll rotation angle of the positioning arm 1.

[0053] The central bevel gear 13 is fixed to the base B so as not to rotate relative to the base B.

[0054] A pair of rotating bevel gears 14 may be meshed at both sides of the central bevel gear 13 , respectively, and rotate relative to a specific position of the gear box 111 .

[0055] Based on the above structure, the plurality of bevel gears 13 and 14 will not move relative to each other when the connecting rod assembly 11 pitches and rotates (see Figure 5 ), when the connecting rod assembly 11 rolls and rotates, they can mesh and rotate with each other (refer to Figures 6 to 8 ). The plurality of bevel gears 13, 14 may have a transmission ratio of 1:1, for example.

[0056] The rotating body 15 can be connected to one or more of the plurality of bevel gears 13 and 14 and rotate together with the bevel gears 13 and 14. For example, a pair of rotating bodies 15 can be respectively fixed to a pair of rotating bevel gears 14 and respectively rotate together with the pair of rotating bevel gears 14 relative to the gear box 11. The rotating body 15 can include a cam 151 and a connection port 152, wherein the cam 151 is fixed to the connecting shaft portion 16 and rotates at the same angle as the corresponding rotating bevel gear 14; the connection port 152 is separated from the connecting shaft portion 16 and rotatably provided on the cam 151. The compensation steel wire 174 described later can be connected to the connection port 152.

[0057] The connecting shaft portion 16 may be formed between the pair of rotating bevel gears 14 and the pair of rotating bodies 15 corresponding thereto, respectively, and the connecting rod assembly 11 is provided on the connecting shaft portion 16 in a manner rotatable in one direction.

[0058] The gravity torque compensating unit 17 can provide a compensating torque, the direction of which is opposite to the direction of the gravity torque of the self-weight of the connecting rod assembly 11 acting on a point. For example, the gravity torque compensating unit 17 can change the length of the elastic body 171 along with the rolling rotation and / or pitching rotation of the connecting rod assembly 11, thereby providing the compensating torque. For example, the gravity torque compensating unit 17 can include a pair of elastic bodies 171, a support platform 172, a pair of sliders 173, and a pair of compensation steel wires 174.

[0059] As shown in the figure, the pair of elastic bodies 171 can be compression springs, but it is not necessarily limited to this. It should be understood that a person skilled in the art can use a variety of other well-known elastic means besides compression springs.

[0060] The support platform 172 may be located on one side of the pair of elastic bodies 171 to support the ends of the pair of elastic bodies 171. The support platform may include a support portion (1721, see Fig.12a and Figure 12b ). The supporting portion 1721 serves to contact the compensation steel wire 174 to receive the compensation torque transmitted from the compensation steel wire 174. For example, the supporting portion 172 may be a roller, thereby not hindering the movement of the compensation steel wire 174. On the one hand, the supporting platform 172 may slide relative to the pitch link 112, thereby also interacting with the gravity torque adjustment portion 18, which will be described later.

[0061] The pair of sliders 173 may be located on the other side of the pair of elastic bodies 171. In other words, the support platform 172 and the slider 173 are located on both sides with the elastic body 171 as a reference. The pair of sliders 173 may slide relative to the pitch link 112, respectively, so that the deformation amount of the elastic body 171 can be determined according to the change in the spacing between the support platform 172 and the slider 173, thereby changing the tension applied to the compensation steel wire 174.

[0062] One side of a pair of compensation steel wires 174 can be fixed on a pair of rotating bodies 15, respectively, and the other side can be fixed on a pair of sliders 173, respectively. The rotation angle of the rotating body 15 can be linked by the compensation steel wires 174, thereby adjusting the position of the pair of sliders 173. In addition, the compensation steel wires 174 can pass through the support platform 172, so that the partial tension applied to the compensation steel wires 174 can provide a torque for rotating the support platform 172 along the pitch direction. In summary, according to the distance between the pair of sliders 173 and the support platform 172, the compensation torque provided by the compensation steel wires 174 to the support platform 172 and the pitch link 112 connected thereto can be changed.

[0063] The gravity torque adjustment unit 18 can reduce the difference between the gravity torque and the compensation torque generated along with the translation distance of the translation link 114. The gravity torque adjustment unit 18 can reduce the elastic potential energy of the elastic body 171 when the translation link 114 translates toward the remote center of motion (RCM) (i.e., when the moment of inertia of the link assembly 11 decreases); and increase the elastic potential energy of the elastic body 171 when the translation link 114 translates toward a direction away from the remote center of motion (RCM) (i.e., when the moment of inertia of the link assembly 11 increases). The gravity torque adjustment unit 18 can include an adjustment steel wire 181 and a speed change means 182.

[0064] The adjustment steel wire 181 can connect the translation link 114 and the support platform 172, so that the support platform 172 can slide when the translation link 114 translates. For example, the adjustment steel wire 181 can include a first adjustment steel wire 1811 connected between the translation link 114 and the speed change means 182; and a second adjustment steel wire 1812 connected between the speed change means 182 and the support platform 172.

[0065] The speed change means 182 is provided on the adjustment steel wire 181, and increases or decreases the sliding distance of the support platform 172 relative to the pitch link 112 in proportion to the translation distance of the translation link 114 with respect to the parallel link 115. For example, the speed change means may include a first reel 1821 for winding the first adjustment steel wire 1811, a second reel 1822 for winding the second adjustment steel wire 1812, and a speed reducer 1823 for rotating the second reel 1822 relative to the first reel 1821 at a set rotation ratio.

[0066] Among them, if Fig.12a and Fig.13 As will be described later, the set rotation ratio is a set rotation ratio that can minimize the difference between the gravity torque and the compensation torque in consideration of given design specifications such as the elastic modulus of the elastic body 171 .

[0067] Meanwhile, the positioning arm 1 can be used as a slave manipulator of a master-slave surgical system. For example, the positioning arm 1 can also include a rolling rotation motor Mr for rolling the connecting rod assembly 11, a pitching motor Mp for pitching the connecting rod assembly 11, and a translation motor Mt for translating the translation connecting rod 114.

[0068] For example, the roll rotation motor Mr can be connected to the base B to roll the gear box 111. The pitch rotation motor M_p rotates together with the gear box 111 and can pitch the pitch link 112 relative to the gear box 111. The translation motor M_t can be installed on the parallel link 115 and translate the translation link 114 relative to the parallel link 115. For example, the parallel link 115 may include a screw shaft 1153 capable of moving the translation link 114 in a ball screw manner.

[0069] Figure 5 is a diagram showing the pitch rotation of a positioning arm according to an embodiment. For ease of understanding, Figure 5 The gear box 111 is omitted.

[0070] Before we proceed, first, refer to Figure 5 The coordinate system shown is used to explain the coordinate system recorded in all the drawings in this specification. First, the x0, y0, z0 coordinate system is a global coordinate system fixed to the bottom B. The x1, y1, z1 coordinate system is a coordinate system that rotates the roll rotation angle θ1 with the z0 axis as the reference; the x2, y2, z2 coordinate system is a coordinate system that rotates the pitch rotation angle θ2 with the y1 axis as the reference. The origin positions of the three coordinate systems are the center of gravity of the roll rotation and pitch rotation of the connecting rod assembly 11. Therefore, the x2, y2, z2 coordinate system can be understood as a local coordinate system fixed to the pitch link 112.

[0071] Reference Figures 1 to 5 When the pitch link 112 pitches and rotates by an angle of θ2 in the x1, y1, z1 coordinate system, that is, when the pitch link 112 pitches and rotates relative to the gear box 111 with the connecting shaft 16 of the pair of bevel gears 14 as the center, the pair of rotating bevel gears 14 are meshed with the fixed central bevel gear 13, so that no relative movement occurs.

[0072] As a result, when the link assembly 11 is pitched and rotated, as the angle between the rotating body 15 and the pitch link 112 increases, the angle between the connection port 152 and the support platform 172 increases. As a result, the slider 173 is pulled to the support platform 172 side by the tension of the compensation steel wire 174, and as a result, the elastic body 171 is compressed, so that the tension applied to the compensation steel wire 174 increases by an amount equivalent to the elastic force of the elastic body 171. As mentioned above, the tension applied to the compensation steel wire 174 can provide a compensation torque in the opposite direction to the gravity torque caused by the weight of the link assembly 11. The gravity compensation process caused by the posture change caused by the pitch rotation can refer to the existing research paper "Static balancing of a manipulator with hemispherical work space", Advanced Intelligent Mechatronics (AIM), 2010 IEEE / ASME International Conference on ("Static balancing of a manipulator with hemispherical work space", 2010 IEEE / ASME International Conference on Advanced Intelligent Mechatronics).

[0073] Figures 6 to 8 FIG. 2 is a diagram showing the rolling rotation of a positioning arm according to an embodiment. Figure 6 The figure shows the rotation directions of the pair of rotating bevel gears 14 and the rotating body 15 when the connecting rod assembly 11 is rotated around the z1 axis. Figure 7 and Figure 8 The figure shows how the link assembly 11 changes when it is actually rolled by the angle θ1.

[0074] Reference Figures 6 to 8 When the gear box 111 rolls and rotates with respect to the bottom B around the connecting shaft of the central bevel gear 13, the pair of rotating bevel gears 14 revolve around the z_0 axis, which is the central axis of the fixed central bevel gear 13, at the same rolling rotation angle θ1 as the gear box 111. As a result, the pair of rotating bevel gears 14 rotate around the y_1 axis, which is the central axis of the pair of rotating bevel gears 14, in opposite directions by angles θ1m and θ2m, respectively.

[0075] Therefore, in Figure 8 The rotating body 15 located on the left side in Figure 7 As a result, the elastic potential energy of the elastic body 171 corresponding to the rotation to the right changes, thereby changing the compensation torque T2 acting in the clockwise direction with respect to the z0 axis.

[0076] Similarly, in Figure 8 The rotating body 15 located on the right side in Figure 7 As a result, the elastic potential energy of the elastic body 171 corresponding to the rotation to the left changes, thereby changing the compensation torque T1 acting in the counterclockwise direction with respect to the z0 axis.

[0077] In general, the total torque of the compensation torque T1 and T2 can compensate for the gravity torque. The gravity compensation process caused by the posture change caused by the rolling rotation can refer to the existing research paper "Static balancing of a manipulator with hemispherical work space", Advanced Intelligent Mechatronics (AIM), 2010 IEEE / ASME International Conference on ("Static balancing of a manipulator with hemispherical work space", 2010 IEEE / ASME International Conference on Advanced Intelligent Mechatronics).

[0078] Above, refer to Figures 5 to 9 , the principle of providing compensation torque according to the change of the roll rotation angle θ1 and the pitch rotation angle θ2 of the connecting rod assembly 11 is explained. However, as shown in the embodiment in the figure, even if the roll rotation angle θ1 and the pitch rotation angle θ2 of the connecting rod assembly 11 do not change, when a part of the accessories (114: translation link) constituting the connecting rod assembly 11 moves relative to other accessories, the length of the lever arm from the origin to the overall center of gravity of the connecting rod assembly 11 will change. Therefore, referring to the content of the existing research paper, it is impossible to compensate for the gravity torque based on this change. Next, the gravity torque adjustment unit 18 that can reduce the difference between the gravity torque and the compensation torque in the above case is explained.

[0079] Fig. 9 and Fig.10 FIG. 1 is a diagram showing the operation of a gravity torque adjustment unit of a translation link during translation according to an embodiment. Fig. 9 It is part of the positioning arm. Figure 1 The front view of the state, Fig.10 The translation link is Fig. 9 FIG. 2 is an illustration of a state in which the device is in a state away from the remote center of rotation (RCM).

[0080] Reference Fig. 9 and Fig.10According to one embodiment, the structure of the positioning arm 1 is that as the translation link 114 moves away from the remote center of motion (RCM), that is, as the moment of inertia of the link assembly 11 relative to the origin increases, the support platform 172 connected to the adjustment steel wire 181 slides in a direction away from the origin. As a result, the distance between the slider 173 and the support platform 172 is shortened, and as a result, the deformation of the elastic body 171 increases. And, from a point (the point where the roll rotation axis and the pitch rotation axis intersect) to the support portion (172, refer to Figure 2 ) will increase by an amount equivalent to the rising distance of the support platform 173. As the distance h increases, the arm length of the compensation torque provided by the compensation steel wire 174 to the link assembly 11 increases. As a result, the compensation torque increases as the translation link 114 moves away from the remote center of motion (RCM), and thus, the gravity torque adjustment unit 18 can reduce the difference between the gravity torque that changes with the translation of the translation link 114 and the compensation torque.

[0081] According to the above embodiments, a compensation torque that changes in accordance with the change of the gravity torque of the three movements, namely, rolling rotation, pitching rotation and translation, can be provided. Below, the effectiveness of the compensation torque generated with the three movements is theoretically explained through a conceptual diagram, and further, the structure and / or conditions that can more accurately compensate for the change of the gravity torque are explained.

[0082] Fig.11 is a conceptual diagram of a positioning arm according to an embodiment. Fig.11 The gravity torque adjustment unit 18 is omitted.

[0083] Reference Fig.11 , the positioning arm 1 according to an embodiment can be shown by a model, in which three mass bodies m1, m2, and m3 connected in a slidable manner move relative to the origin O. At this time, (i) the first mass body m1 corresponds to the pitch link 112; (ii) the second mass body m2 corresponds to the parallel link 115, the connecting rod 116, the gravity torque compensation part 17, and the gravity torque adjustment part 18; (iii) the third mass body m3 corresponds to the translation link 114. The center of gravity distances of the three mass bodies m1, m2, and m3 are l1, l2, and l3, respectively.

[0084] Furthermore, the elastic body 171 is shown by a zero-length spring model, and the elastic modulus is k. For those skilled in the art, it should be understood that the zero-length spring model can be implemented in the manner of the above illustrated embodiment.

[0085] On the one hand, h1, h and b are defined as follows:

[0086] -h1: The distance from the origin O to one end of the zero-length spring model in the x1-z1 plane coordinate system

[0087] -h: The distance from the origin O to the other end of the zero-length spring model in the x1-z1 plane coordinate system

[0088] -b: The distance from the other end of the zero-length spring model k to the second mass body m2 in the x1-z1 plane coordinate system

[0089] Here, h1 is a constant, which is the same as the distance from the connecting shaft 16 to the connecting port 152. h is a variable, which is the initial value h1 plus the translation distance of the support platform 172 relative to the pitch link 112 (Δh=Δl2). b is a constant obtained by subtracting the variable h from the distance l2 of the center of gravity of the second mass body m2.

[0090] First, in order to compensate for the gravitational torque during pitch rotation, the sum of the overall potential energy of the positioning arm 1 should be a constant that is not affected by the pitch rotation angle θ2. When the sum of the three mass bodies m1, m2, and m3 is set to m, and the total center of gravity distance of the three mass bodies m1, m2, and m3 is set to 1, as shown in the following formula 1, the sum of the overall potential energy of the positioning arm 1 is expressed as the sum of the elastic potential energy and the gravitational potential energy.

[0091] Formula 1

[0092]

[0093] It can be seen that we first need to start from the first item of the result obtained by sorting out formula 1 to satisfy Substituting the centroid formula into the above conditions, we get the following formula 2.

[0094] Formula 2

[0095]

[0096] It can be seen from Formula 2 that the change Δl3 of the distance l3 of the center of gravity of the third mass body m3 should be proportional to the change of h (Δh=Δl2) defined above (Δl2∝Δl3). In other words, in the adopted structure, the translation distance of the translation link 114 relative to the pitch link 112 is proportional to the translation distance of the support platform 172 relative to the pitch link 112. According to the embodiment, it can be seen that the corresponding conditions can be met.

[0097] Fig.12a and Fig.13 2 is a diagram illustrating a gravity torque adjustment unit according to an embodiment.

[0098] Reference Fig.12a and Fig.13The gravity torque according to the roll rotation angle θ_r and the pitch rotation angle θ_p is calculated by the following formula, and the elastic constant k of the elastic body 171 and the set rotation ratio (c) of the reducer 1823 that meet the requirements can be determined as the reduction ratio.

[0099] First, the terms used in each formula are as follows, and the parts that overlap with the terms explained above are omitted. Fig.13 In the following formula, M_1, M_2, M_3, M_4 and M_b correspond to the pitch link 112, the connecting rod 116, the parallel link 115, the translation link 114 and the support platform 112 respectively, and H_i is the height from the origin to the center of gravity of each M_i.

[0100] a i :M i The distance between the center of mass and the center of rotation

[0101] h1: The force arm of the cone gravity compensation part (fixed)

[0102] h: The force arm of the cone gravity compensation part (change)

[0103] c: 1 / (transmission ratio)

[0104] d: translation length (0 <d<150mm)

[0105] x: compressed length of the spring

[0106] θ 1m : Rotation angle of bevel gear (1)

[0107] θ 2m : Rotation angle of bevel gear (2)

[0108] k: elastic constant of gravity compensation part

[0109] τ g,r : Gravity torque (rolling)

[0110] τ g,p : Gravity torque (pitch)

[0111] τ k,r :Compensation torque (rolling)

[0112] τ k,p :Compensation torque (pitch)

[0113] τ r : Total torque (rolling)

[0114] τ p : Total torque (pitch)

[0115] V k(q): potential energy of the gravity compensation part for q (1-degree of freedom)

[0116] V k,total : The total potential energy of the system

[0117] Next, the formula for calculating the gravity torque based on the roll rotation angle θ_r and the pitch rotation angle θ_p is as follows.

[0118] U i =M i ga i

[0119]

[0120] H i =a i cos(θ r )cos(θ p )

[0121]

[0122]

[0123] h=h init +c*d

[0124] θ 1m =-θ p -θ r -π

[0125] θ 2m =-θ p +θ r -π

[0126] x(q)=h1 2 +h 2 +2h1h*cos(q)

[0127] V k，total =V k (θ 1m )+V k (θ 2m )

[0128]

[0129]

[0130] τ r =τ g，r +τ k，r =0

[0131] τ p =τ g，p +τ k，p =0

[0132]

[0133] Through the above-mentioned development process, the elastic modulus of the elastic body 171 and the calculation process of the setting rotation ratio of the speed reducer 1823 are finally determined as follows.

[0134]

[0135] As described above, by changing the elastic modulus of the elastic body 17 and / or the setting rotation ratio of the reducer 1823 according to other design specifications, the difference between the gravity torque and the compensation torque can be reduced, and a more effective gravity compensation device can be provided.

[0136] Although some embodiments of the present invention have been shown and described, the present invention is not limited to the described embodiments. On the contrary, it will be appreciated by those skilled in the art that these embodiments may be changed without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the claims and their equivalents.

Claims

1. A positioning arm, characterized in that: include: A link assembly having a translation link that can translate along a virtual axis passing through a remote center of motion (RCM) at a specified distance from a point, and can rotate in at least two directions about the point; a gravity torque compensating portion, which provides a compensating torque, the direction of which is opposite to the direction of the gravity torque caused by the own weight of the connecting rod assembly acting on the point; and A gravity torque adjustment portion reduces a difference between the gravity torque generated along with a translation distance of the translation link and the compensation torque.

2. The positioning arm according to claim 1, characterized in that: The link assembly can roll and pitch, and the translation link is not affected by the roll and pitch angles and can translate along a virtual axis passing through the remote motion center.

3. The positioning arm according to claim 2, characterized in that: The connecting rod assembly further comprises: A gear box, which can roll and rotate relative to the base; a pitch link, which is rotatable in pitch relative to the gearbox; a parallel link movable in a posture parallel to the length direction of the pitch link; and a connecting rod connecting the pitch link and the parallel link, The translation link is translatable along a guide located on the parallel link.

4. The positioning arm according to claim 3, characterized in that: Also includes: A central bevel gear fixed to the bottom; a pair of rotating bevel gears, which are respectively meshed on both sides of the central bevel gear and can rotate relative to the gear box; as well as A pair of rotating bodies are respectively fixed to the pair of rotating bevel gears and can rotate relative to the gear box together with the pair of rotating bevel gears.

5. The positioning arm according to claim 4, characterized in that: A connecting shaft portion is formed between the pair of rotating bevel gears and the pair of rotating bodies corresponding thereto, respectively, and the connecting rod assembly is arranged on the connecting shaft portion in a manner that it can rotate in one direction.

6. The positioning arm according to claim 4, characterized in that: The pair of rotating bevel gears will not move relative to each other when the connecting rod assembly rotates in pitch, and will rotate in opposite directions relative to the same axis when the connecting rod assembly rotates in roll.

7. The positioning arm according to claim 4, characterized in that: The gravity torque compensation unit comprises: A pair of elastic bodies changes length according to the rolling rotation or the pitching rotation of the link assembly, thereby providing elastic force for generating the compensation torque.

8. The positioning arm according to claim 7, characterized in that: The gravity torque compensation unit further includes: a support platform, which is located on one side of the pair of elastic bodies; a pair of sliders, located on the other side of the pair of elastic bodies and slidable relative to the pitch link; and A pair of compensating steel wires have one side fixed to the pair of rotating bodies and the other side fixed to the pair of sliding blocks.

9. The positioning arm according to claim 8, characterized in that The support platform includes a support portion, which is arranged on the side of the path through which the pair of compensation steel wires pass, and functions to receive the compensation torque from the pair of compensation steel wires. The gravity torque adjustment unit lowers the support platform when the translation link translates toward the remote motion center, thereby reducing the lever arm length of the compensation torque; and raises the support platform when the translation link translates in a direction away from the remote motion center, thereby increasing the lever arm length of the compensation torque.

10. The positioning arm according to claim 9, characterized in that The support platform is arranged to be slidable relative to the pitch link. The gravity torque adjustment part includes an adjustment steel wire, which connects the translation link and the support platform to each other, so as to slide the support platform when the translation link translates.

11. The positioning arm according to claim 10, characterized in that The gravity torque adjustment unit further includes a speed change means for increasing or decreasing a sliding distance of the support platform relative to the pitch link in proportion to a translation distance of the translation link relative to the parallel link.

12. The positioning arm according to claim 11, characterized in that The adjustment wire includes a first adjustment wire and a second adjustment wire connected to one side and the other side of the speed change means, respectively. The speed changing means comprises: A first reel, on which the first adjustment steel wire is wound; a second reel on which the second adjustment wire is wound; and A speed reducer causes the second drum to rotate relative to the first drum at a set rotation ratio.

13. A positioning arm, characterized in that: include: a linkage assembly capable of roll and pitch rotation and having a translation link capable of translation along a virtual axis passing through a remote center of motion (RCM) a specified distance from a point; and A plurality of bevel gears, which do not move relative to each other when the connecting rod assembly pitches and rotates, and mesh and rotate when the connecting rod assembly rolls; a rotating body connected to at least one of the plurality of bevel gears and rotating together with the connected bevel gear; and a gravity torque compensating portion connected to the rotating body and deforming the elastic body with the rolling rotation and pitching rotation of the connecting rod assembly, thereby providing a compensation torque, the direction of which is opposite to the direction of the gravity torque due to the self-weight of the connecting rod assembly; The positioning arm further includes a gravity torque adjustment portion, which increases or decreases the length of the force arm of the compensation torque according to the translation of the translation link, thereby reducing the difference between the gravity torque and the compensation torque.

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