EP3523098A1

EP3523098A1 - Robotic structure with six degrees of freedom allowing gripping

Info

Publication number: EP3523098A1
Application number: EP17786969.0A
Authority: EP
Inventors: Redwan DAHMOUCHE; Wissem HAOUAS
Original assignee: Universite de Franche-Comte
Current assignee: Universite de Franche-Comte
Priority date: 2016-10-06
Filing date: 2017-09-29
Publication date: 2019-08-14
Also published as: US20200039091A1; FR3057191A1; FR3057191B1; WO2018065702A1; JP2019530586A

Abstract

The present invention relates to a parallel robotic structure (1) with six degrees of freedom which comprises movable bases (2, 21, 22, 23, 24, 25, 26, 27, 21', 22', 23', 24', 25', 26', 27', 28') that can be rotated or translated, and a platform (3) coupled with the movable bases by moving means, characterised in that the platform (3) is made up of two rigid elements connected to one another by a single articulation. Said novel solution is an original and innovative parallel robotic structure (1) which makes it possible to perform cutting, gripping and handling operations simultaneously with six degrees of freedom without requiring an additional tool. The gripping functionality is provided by the articulated platform which is an integral part of the mechanical architecture and can be entirely controlled by the offset actuators located in the stationary base.

Description

ROBOTIC STRUCTURE WITH SIX DEGREES OF FREEDOM ALLOWING

PREHENSION

Technical area

The present invention relates to a robotic structure parallel to at least six degrees of freedom for gripping and handling particularly for micro-nano-manipulation.

From a structural point of view, industrial manipulative robots can be classified into two categories: serial robots and parallel robots. Serial robots, known as manipulator arms, are the most widespread in the industry and are characterized by an open kinematic chain (a series of actuators, links and arms) that runs from the base of the robot to the wrist. Parallel robots are characterized by several parallel kinematic chains connected from the base to the platform.

The advantage of parallel robots over serial robots is that they have greater rigidity and the ability to attach the actuators to the base of the robot to lighten the moving parts. The consequence is that the masses transportable by the robot are larger and the accelerations stronger. The preferred applications are fast grip and move applications as described in WO 87/03 528 or the displacement of heavy loads such as pilot cabs in flight simulators as described in US Pat. No. 3,295,224.

In most parallel robots, the platform consists of a rigid body. However, some particular robots have an articulated platform. US Patent No. 6,516,681 describes a robot of this type which has four degrees of freedom at most, three in translation and one in rotation. The rotation of the tool is achieved through the reconfiguration of a platform consisting of three elements articulated by pivot links. A similar robot limited to the same degrees of freedom but with a Parallelogram as a platform is described in EP 1 870 214. Note that the robots described in the patents cited above have been very successful and have been widely marketed.

Depending on the application, the operations performed by the robots require the use of adequate electrical, hydraulic or pneumatic tools (pliers, etc.) attached to the cuffs of the serial robots or on the platforms of parallel robots (including robots mentioned above). Although this configuration is adequate in a number of applications, it has limitations especially in applications that have high constraints of space, a need for miniaturization and / or to lighten the displaced masses as much as possible.

In this invention, functions such as gripping, manipulation in the six degrees of freedom of space and cutting by exmples are provided by a parallel robotic mechanism without the addition of additional powered tools, and this through a articulated platform. Thus, the robotic structure according to the invention makes it possible on the one hand to overcome the electrical, pneumatic or hydraulic connections necessary for the actuation of any tools and on the other hand to reduce the bulk and the mass at the level of the platform of the robot which facilitates its miniaturization. In addition, the structure of the robot allows to place the actuators away from the platform, including using cables, thus making the structure even more compact.

The preferred applications are applications with high congestion constraints such as minimally invasive surgery in the biomedical field where the robot must be inserted into the human body through a tube or an endoscope. Furthermore, the miniaturization capacity of the robotic structure according to the invention (the structure can be manufactured at the micrometric scale) makes it particularly suitable for high precision and high-speed handling including millimeter components (watch components, electronics, etc.), micrometric (Micro-ElectroMacatronic Systems, MOEMS, etc.) and even nanoscale (nanowires, nanotubes, etc.) can exceed the handling accuracy and production rates of existing systems. Finally, the robot, which is characterized by six degrees of freedom in translation and rotation in addition to the configurable platform that gives it additional degrees of freedom, makes it one of the most versatile and dexterous robots that exist at today, especially for the manipulation of very small size components. The object of the invention is thus to propose a new robotic structure that simultaneously allows grasping and manipulation with six degrees of freedom and cutting by example without the use of a gripper or an additional powered tool.

The parallel robotic structure with six degrees of freedom according to the invention comprises mobile bases that can be actuated in rotation or in translation and a platform coupled to the mobile bases by means of setting in motion it is characterized in that the platform consists of two rigid elements connected to one another by a single link. This new solution is an original and innovative parallel robotic structure that simultaneously allows gripping, cutting and manipulation operations with six degrees of freedom without the need for an additional powered tool. The gripping functionality is ensured by the articulated platform which is part of the mechanical architecture itself and can be fully controlled by the remote actuators located in the fixed base.

This structure allows the positioning according to the six degrees of freedom in the space of a platform composed of two rigid rigid elements. These two movable elements are connected to each other so as to be able to rotate and / or translate one of the moving elements relative to the other around or along one or more axes that can be exploited for carrying out various tasks ( gripping, handling, cutting, etc.) thanks to a single link. The two mobile elements of the platform are connected to several, for example seven, third struts so rigid. Each third spacer is connected at its other end to a second spacer rigidly or by means of a ball joint, a pivot or a universal joint. Each second spacer is connected at its other end to a first spacer rigidly or by means of a ball joint, a pivot or a universal joint. Each first spacer is connected to a mobile base and can translate along or rotate about an axis at a minimum. The moving of the first spacers can be carried out by means of one or more actuators connected to the mobile bases rigidly or through the passive links and / or flexible links and / or cables. The fixed part of the actuators are connected to the base element by means of a rigid or passive or flexible connection. The assembly is arranged in such a way that the positions and the orientations of the mobile elements of the platform in the space as well as the distance and / or the angle between the two mobile elements can be controlled by the movements of the actuators driven by a management computer. Degrees of freedom beyond 6 are used to perform particular tasks such as gripping, cutting, etc. If the number of arms is greater than seven this allows to obtain more degrees of freedom in the platform and / or additional redundancies of actuation and / or measurement. On the other hand, a redundant actuation device makes it possible to increase the working space, to limit the presence of kinematic singularities, to control the internal stresses in the kinematic chain of the device, to increase the forces and torques transmitted to the elements. their speeds and accelerations.

Advantageously, the link is a pivot link.

Advantageously, the mobile bases are arranged symmetrically. A symmetrical robot makes it possible to homogenize the dimensions of the parts, to simplify the design, the modeling, the manufacture and the control of the device.

According to one particular arrangement, the means for moving the spacers connected by passive joints on the one hand to the articulated platform and secondly to a mobile base are linear actuators. The fixed parts of the actuators are, for example, rigidly connected to a base element which allows to lighten the moving parts of the device. This has repercussions on the moving elements by a gain in speed, acceleration and applicable effort (makes it possible to transport important loads). The passive links can be replaced by flexible links which makes it possible to manufacture the device on a miniaturized scale (millimetric, micrometric). Indeed, this eliminates the games that can exist in the classic leashes (pivot, kneecap, carding, etc.) and which are a source of performance degradation (repeatability, accuracy, etc.).

Advantageously, the passive joints are ball joints, pivots or universal joints. The translations and rotations of the movable elements can be obtained solely from translations of the actuators which allows a gain in compactness and accuracy. The actuators can be deported away from the moving elements (by means of cables or bars for example) in order to obtain very compact systems that are useful in applications with high congestion constraints (medical, nuclear, aerospace, etc.).

Advantageously, the structure comprises force sensors arranged on the mobile bases. This makes it possible to self-calibrate the robot on which the structure is mounted, to simplify the calculation of the positions and orientations of the moving elements and to improve the precision of their movements. The forces are transmitted from the actuators to the mobile elements for measuring and / or controlling the forces and torques applied by the moving elements on their environment.

Advantageously, the structure comprises position sensors arranged on the actuators.

Advantageously, the structure is of sub-millimetric size. The structure can thus be used for micro-nano-manipulation and micro-nano-assembly as well as handling in confined spaces (endoscopes, minimally invasive surgeries). The structure can be manufactured at macrometric scales (greater than the sizes of conventional robots), miniaturized (endoscopy for example) or micrometric (micro-nanomanipulation for example). The millimetric structure can be composed of micrometric elements, it could also be centimeter size or even larger and carry out micro-nano manipulation tasks. For example, it can be applied for:

the assembly of nano-sensors, optical fibers, semiconductors,

the testing, control and characterization of micro-nano-objects, the precise assembly of optical systems such as interferometers,

the manipulation of biological cells,

assembly in watch industries,

minimally invasive surgery (instrumented endoscope of a forceps

6 degrees of freedom).

Advantageously, the structure is actuated by actuators in translation (linear motors, electric or hydraulic cylinders, etc.), in rotation (electric motors, etc.) or less common actuators (piezoelectric, electrostatic, thermal, etc.). possibly having several degrees of freedom (XY tables, piezotubes, etc.).

Compared with existing robotic structures, the invention has the following characteristics:

The gripping and / or cutting functionality is integrated into the structure and actuation performed from the actuators placed on the base member.

The masses and the inertia of the structure at the micrometric scale are very low, allowing much lower cycle times than current systems. The accuracy can go below the micrometer (limit of current parallel structures) and even go to the nanoscale.

The cost of manufacturing the system is much lower than existing systems.

It is possible to perform micro-nano-manipulations and assemblies with six degrees of freedom and operations inside confined spaces (human body, scanning electron microscope, ...).

Passive joints can be replaced by flexible links guaranteeing high repeatability of the structure and / or biocompatibility.

With the integration of the force sensors on the mobile bases the forces applied on the terminal member can be measured without using connections (wires, pipe, etc.) on the platform. With the integration of position sensors on the different actuators, a self-calibration of the robot can be realized.

The absence of electrical connectors on the operational parts of the structure allows manipulation in constrained environments where the use of electronic compounds is limited / prohibited (liquids, human cops, etc.).

In summary, the system can be more accurate, faster and less expensive than existing solutions.

The solution requires very small amounts of material and can be mass produced with high added value. The system is manufactured by standard processes and does not require the use of any hazardous substances.

Other advantages may still appear to those skilled in the art on reading the examples below, illustrated by the appended figures given by way of example: Brief description of the figures

FIG. 1 is an arrangement graph of a first structure; FIG. 2 represents an arrangement graph of a second structure;

FIG. 3 is an example of the first robotic structure of FIG. 1,

FIG. 4 is an example of the second robotic structure of FIG. 2,

FIG. 5 is another example of structure with four spacers per arm,

FIG. 6 is another example of structure with a spacer with several branches,

Figure 7 is a variant of Figure 2 where the actuators are arranged between two links.

Figures 1 and 2 show the arrangement graphs of two different robotic structures. These graphs highlight the topology of the robot structure and the various branches and kinematic loops. The conventions used for these graphs are:

A: Passive connection of Universal (cardan) or spherical (ball) type.

R: Passive type Rotoid link (pivot)

Qi: Actuator with 1 degree of freedom.

These examples of structures are part of the family of manipulators with six degrees of freedom and more of which some variants are redundant in operation.

The example illustrated in Figure 3 shows a robotic structure 1 with seven movable bases 2, an articulated platform 3 in two parts 30 and 31 connected by a passive connection 32. Each of the two parts 30 and 31 is extended by a gripper 33; this gripper can be replaced by scissors, pliers or others. Three mobile bases 21, 22, 23 are connected to the part 31 of the articulated platform 3 by an arm 4 and, in the same way, three bases 24, 25, 26 are connected to the part 32 of the articulated platform 3 by an arm 4.

Each of the arms 4 consists of three spacers 40, 41 and 42, the first spacer 40 is connected to the second spacer 41 by a passive connection 400, the second spacer 41 is connected to the third spacer 42 by a passive connection 410. Passive link 400 may be of spherical type and link 410 of universal type.

Actuators Qi are arranged on the spacers 40.

The movements of the parts 30 and 31 of the articulated platform 3 as well as the relative movement between the two parts of the platform are controlled by the movements of the different arms 4. The opening and / or closing of the grippers 33 is obtained by moving arms and their position and orientation

The example illustrated in Figure 4 shows a robotic structure 1 substantially identical to the previous except that it comprises eight mobile bases 2 instead of seven which makes it a redundant robot actuation.

Here four bases 21 ', 22', 23 ', 24' are connected to the part 31 of the articulated platform 3 by an arm 4 and, in the same way, four bases 25 ', 26', 27 ', 28' are connected to the part 32 of the articulated platform 3 by an arm 4.

Actuators Qi are arranged on the spacers 40.

The movements of parts 30 and 31 of the articulated platform 3 as well as the relative movement between the two parts of the platform are controlled by the movements of the different arms 4. In the example illustrated in FIG. 5, each arm 4 consists of four spacers 40,

41, 42, 43 connected by three joints 400, 410, 430. The actuators are Controlled by a command 6. This structure makes it possible to use links that are simpler to produce and therefore less expensive while being more precise and offering a greater range of movement.

Figure 6 shows a structure where the arms 4 comprise a spacer 44 with several branches 440, 441, 442. Here the spacer 44 has three branches but it could have two or more. This structure is simpler because it requires fewer actuators, here two actuators with three degrees of freedom at least Q1, Q2 and an actuator with at least one degree of freedom Q7.

In the variant of Figure 7, the actuators Qi are disposed between the two passive links 400 and 410.

Claims

1. A six-degree parallel robotic structure (1) comprising movable bases (2, 21, 22, 23, 24, 25, 26, 27, 21 ', 22', 23 ',

24 ', 25', 26 ', 27', 28 ') being able to be actuated in rotation or in translation and a platform coupled to the mobile bases by movement means characterized in that the platform (3) consists of two rigid elements connected to each other by a single link.

2. Structure (1) according to claim 1, characterized in that the connection is a pivot connection (32).

3. Structure (1) according to one of the preceding claims, characterized in that the movable bases (2, 21, 22, 23, 24, 25, 26, 27, 21 ',

22 ', 23', 24 ', 25', 26 ', 27', 28 ') are arranged symmetrically

4. Structure (1) according to one of the preceding claims, characterized in that the means for moving the spacers (40, 41, 42) connected by passive joints (400, 410) on the one hand to the articulated platform ( 3) and on the other hand to a movable base (2, 21, 22, 23, 24, 25, 26, 27, 21 ', 22', 23 ', 24', 25 ', 26', 27 ', 28 ') are linear actuators.

5. Structure (1) according to the preceding claim, characterized in that the passive joints (400, 410) are ball joints or cardan joints.

6. Structure (1) according to one of the preceding claims, characterized in that it comprises force sensors disposed on the mobile bases.

7. Structure (1) according to one of the preceding claims, characterized in that it is of sub-millimeter size.

8. Structure (1) according to one of the preceding claims, characterized in that it is actuated by piezoelectric actuators Qi.

9. Structure (1) according to one of the preceding claims, characterized in that it comprises position sensors arranged on the actuators