RU2842621C1 - Three-finger gripping device - Google Patents

Abstract

FIELD: robotics.

SUBSTANCE: invention relates to robotics and can be used to design manipulator grips, as well as to medical equipment for upper extremity prostheses. Three-finger gripping device comprises a base with three fingers mounted on it, made in the form of movable phalanxes turning relative to the base and to each other. All three fingers are identical and contain three phalanges. First finger is installed on a bracket rotating relative to the base. Second and third fingers are fixed on base without possibility of rotation and in initial position are located at distance exceeding width of finger. Second finger is fixed on base. Third finger is arranged on said base to displace toward second finger. First phalanxes of all three fingers are installed with possibility of being tilted and manually fixed relative to the housing and the rotary bracket.

EFFECT: improved functional capabilities of the gripper, simplified design, simplified control of the gripper.

1 cl, 7 dwg

Description

The invention relates to robotics and can be used in the creation of grips for manipulators, as well as to medical equipment for upper limb prostheses.

Currently, there are many different designs of gripping devices (grabbers) for manipulators. Grabbers with rigid finger phalanges that are connected to each other by coaxial rotational pairs are known. Maximum controllability of finger movement is ensured by individual mobility of the phalanges, which is ensured by individual, for example, rotary drives built into the phalanges, examples of which are the DEXHAND, DLR Hand II models (https://www.dlr.de) developed at the Institute of Robotics and Mechatronics, Germany, and technical solutions under patents US 2012013139 (2012) and RU 2481942 (2013), or with traction cable drives for each phalanx, such as for the Shadow Hand gripper fingers of the Shadow Hand Company (A. Kochan, “Shadow delivers first hand,” Industrial Robot: an International Journal, vol. 32, no. 1, pp. 15-16, 2005), DLR David HAND developed at the Institute of Robotics and Mechatronics, Germany, and a number of others. It is obvious that such gripping devices are very complex and, accordingly, expensive technical devices that have maximum functionality close to the human hand, often excessive for most technical tasks performed with the help of manipulators.

The "Grip" PM 173229 (2017) is known, which contains a base with five groups of links installed on it, forming three-phalangeal fingers. In general, the design of the grip repeats the structure of the human hand. Like the grips given above, this grip is a complex technical device with structural redundancy, and due to the strong simplification of the mobility of the phalanges of the fingers in favor of simplicity of the design, the functionality of the grip is significantly reduced.

Also known is "Adaptive three-fingered gripping device" RU 2481942, 2013. The gripping device includes a housing with three fingers mounted thereon, located at the vertices of an isosceles or equilateral triangle. Each finger consists of three phalanges, the first of which rotates relative to the housing, and the second and third phalanges rotate relative to the first and second, respectively, using individual rotary drives with parallel rotation axes. Moreover, two fingers can be configured to rotate around an axis perpendicular to the plane of finger installation and perpendicular to the rotation axes of the phalanges. Each of the three fingers is configured to rotate relative to the housing by an angle of at least 90° using an individual drive. A rotary drive is installed in the housing, rotating the housing with fingers relative to the structural element of the housing, with the help of which the gripping device is attached to the manipulator. Servomotors with built-in torque sensing are used as individual drives, and the contact surfaces of the phalanges are equipped with tactile sensors.

The main disadvantage of this gripping device is the rigid installation of the fingers on the base, which significantly limits the size and shape of reliably gripped objects, which include objects close in shape to spherical and cylindrical, and in terms of dimensions close to the distance between the fingers and the size of the fingers themselves, which in turn are determined by the size and configuration of the components of the servo drives, as well as the difficulty of gripping flat objects, cylindrical objects with small diameters. Rigid fixation of the fingers on the base according to the triangular scheme limits the functionality of the gripper, since it is significantly difficult to grip flat objects and it is fundamentally impossible to implement the scheme of "pincer grip" with two fingers of thin objects and objects with a small diameter such as a pencil.

The closest technical solution to the proposed invention, adopted as a prototype, is the gripping device according to patent WO 2004/028753, containing a base with three fingers mounted thereon. One central finger is rigidly mounted on the base and cannot change its orientation relative to it. Each of the other two fingers is mounted on its own rotary bracket. The rotary brackets are mounted on the base so that they can synchronously rotate relative to the base around axes perpendicular to the base from one finger rotation drive, the output gear of which is rigidly connected to the toothed wheels on the rotary brackets through a system of gear wheels. Thus, the fingers can only rotate synchronously and at the same angles. In this case, the axes of rotation of the phalanges of the fingers can be parallel in two extreme positions of the rotary brackets. In one extreme position, the fingers are located parallel to each other, with the extreme rotary fingers located close to the fixed middle finger, and in the other extreme position, when the levers are rotated by 180, the fingers are located according to the two against one pattern. In any intermediate position of the levers, the rotation axes of the phalanges form isosceles triangles of various configurations depending on the angle of rotation of the drive.

The main disadvantage of the prototype is the limited functionality caused by the rotation of both movable fingers through a system of gear wheels by one drive, which leads to equality of the rotation angles of the contact planes of the movable fingers' phalanges relative to the contact planes of the fixed finger, which is favorable for gripping objects symmetrical relative to the axis of the gripping device and significantly complicates the gripping of asymmetric objects, since in this case contact forces arise that are not perpendicular to the axes of mobility of the phalanges, which generate "breakout moments" applied to the hinges of the phalanges, which can lead to the destruction of the fingers at significant working moments in the phalanx drives, and the resulting unbalanced system of contact forces applied to the object can lead to the extrusion of the object from the grip, which greatly complicates the planning and implementation of the process of gripping such objects. At the same time, gripping flat objects is significantly complicated and it is fundamentally impossible to implement the scheme of "pincer grip" with two fingers of thin narrow objects and objects with a small diameter, such as a pencil.

At the same time, the organization of synchronous rotation of two fingers using a system of gear wheels significantly complicates the design and makes it heavier.

It should also be noted that it is difficult to organize the control of such a grip, especially in light of modern methods of controlling anthropomorphic grips of manipulators using setting devices (copying gloves) put on the operator's hand, with the help of which he controls the grip by simulating the process of gripping an object with the operator's hand, which leads to a change in the kinematics of the setting device and generates control effects on the grip. Obviously, despite the apparent anthropomorphism of the prototype, it is practically impossible to control the rotations of two fingers moving relative to the "palm-body" with the setting device.

The objectives of the claimed invention are:

- increasing the functional capabilities of the capture,

- simplification of the design,

- simplification of capture control.

The task of increasing the functional capabilities of the gripping device is solved by using a design scheme with the implementation of various mutual positions of the fingers "two against one". In this case, the first finger is installed on a bracket rotating relative to the base, the second and third fingers are installed without the possibility of rotation and in the initial position are located at a distance exceeding the width of the finger, wherein the second finger is fixedly fixed to the base, and the third finger is installed on the base with the possibility of displacement in the direction of the second finger.

In the initial position of the swivel bracket, the first finger is located on the same line as the second and third fingers. When the bracket rotates, the first finger rotates relative to the other two and in the extreme position is located strictly opposite them, while the tops of the fingers in the plan form an isosceles triangle.

All three fingers of the gripper can be manually pre-tilted and locked relative to the body and the rotating bracket, thereby ensuring that the fingers cover a given volume, taking into account the expected size and shape of the objects to be worked with.

The rotation of the first finger and the displacement of the third ensures the implementation of a “pincer” grip.

Thus, the task of increasing the functional capabilities of the gripping device is solved by forming various schemes of mutual arrangement of fingers, starting from the “three in a line” scheme and ending with the “two against one” scheme, which allows for a variety of gripping options, including a two-finger “pincer” grip.

The task of simplifying the gripper design is solved by using a three-finger gripper design, which has functional completeness for almost all technical tasks of gripper applications, as well as using the principle of rotary opposition of the thumb of the hand, namely, in contrast to the prototype, providing the ability to rotate only one of the three fingers relative to the base of the gripper, which significantly simplifies the finger rotation mechanism, lightens it and the gripper as a whole.

The task of simplifying the control of the proposed gripping device is also solved by using an anthropomorphic scheme of a three-fingered grip with one rotating finger, since the control of such a gripping device is intuitively easily implemented by the operator with the help of a setting device (glove) put on his hand, repeating the kinematics of the gripping device.

The essence of the invention is explained by the following drawings and figures.

Fig. 1 shows the components of a three-fingered gripping device.

Fig. 2 shows the general arrangement of the mechanisms of the component parts of a three-fingered gripping device.

Fig. 3 shows the range of adjustment of the position of the proximal phalanges of the fingers of the three-fingered gripping device.

Fig. 4 shows the range of positions of the thumb opposition mechanism of the three-fingered gripping device.

Fig. 5 shows the transition to a preset configuration of a three-fingered gripping device that implements a “pincer” grip.

Fig. 6 shows the position of the phalanges of the fingers during a “pincer” grip.

Fig. 7 shows options for gripping a cylindrical object depending on the preset position of the little finger of the three-fingered gripping device.

The three-fingered gripping device is constructed according to the modular principle and consists of three structurally identical fingers 1-3 (Fig. 1), where finger 1 acts as the thumb, finger 2 as the index finger, and finger 3 as the little finger. Fingers 2 and 3 are mounted on the base 4 of the three-fingered gripping device, and thumb 1 is mounted on bracket 5.

Each finger, including thumb 1, consists of three phalanges, with the proximal phalanx of thumb 1 rotating (tilting) relative to axis α-1, the middle phalanx rotating relative to axis β-1, and the distal phalanx rotating relative to axis γ-1. Accordingly, the phalanges of index finger 2 rotate relative to axes α-2, β-2, γ-2, and the phalanges of little finger 3 - relative to axes α-3, β-3, γ-3. Opposition of thumb 1 is achieved by rotating bracket 5 relative to axis δ-5.

The middle and distal phalanges of the fingers are controlled by independent drives. Each drive includes an electric motor 6 (Fig. 2), a control board 7 and a phalanx position sensor 8. The thumb rotation drive 1 consists of an electric motor 9, a transmission mechanism 10 including a spur and worm gear, a control board 11, and a position sensor 12. Power supply to the drives and transmission of information from all sensors of the three-fingered gripping device to the control system is performed through a switching board 13.

The proximal phalanges of the fingers do not have rotation drives. The tilt relative to the axes α-1, α-2, α-3 of the proximal phalanges of all fingers of the three-fingered gripping device is carried out by pre-installation in a fixed position using clamp 14 (Fig. 3), clamped by screws 15, while in the dorsal direction the finger extension angle θ reaches 20°.

The angle of rotation of bracket 5 relative to axis δ-5 is 180° (Fig. 4), which allows to oppose thumb 1 to index finger 2 and little finger 3 (Fig. 5, left). In this position, the three-fingered gripping device allows to combine the specified axis of rotation of the object of manipulation with the axis of rotation passing through the center of the fastening interface of the three-fingered gripping device λ, which can simplify a number of technological operations.

The little finger 3 of the three-fingered gripping device can be manually moved to a position opposite the opposable thumb 1 (Fig. 5, on the right). In this position, the three-fingered gripping device can perform a “pincer” grip (Fig. 6) due to the ability to extend the distal phalanges of the fingers in the dorsal direction by an angle ϕ.

The placement of the little finger 3 in a position opposite the opposing thumb 1 does not deprive the three-fingered gripping device of the ability to perform gripping operations other than the “pincer” type, as shown in Fig. 7.

Claims (1)

A three-finger gripping device comprising a base with three fingers mounted thereon, made in the form of movable phalanges that rotate relative to the base and to each other, characterized in that all three fingers are made identical and contain three phalanges each, the first finger is mounted on a bracket that rotates relative to the base, the second and third fingers are mounted on the base without the possibility of rotation and in the initial position are located at a distance exceeding the width of the finger, wherein the second finger is fixedly fixed to the base, and the third finger is mounted on the base with the possibility of displacement in the direction of the second finger, wherein the first phalanges of all three fingers are mounted with the possibility of tilting and fixing manually relative to the body and the rotary bracket.