Robot with multiple degrees of freedom.

Robot with multiple degrees of freedom

The invention relates to a robot with multiple degrees of freedom comprising multiple legs linked at a first of their ends to a base, and at a second of their ends opposite to the first, ends to a mobile platform, which platform carries at least one tool, and wherein the robot further comprises an actuator for operating the tool or tools.

Such a robot, is known from EP-A-1 870 214. The known robot has a single tool mounted on the mobile platform which is made up of four members linked together by means of articulated linkages. The robot also has four legs and is thus provided with four degrees of freedom pertaining to the movement of the tool. The tool itself has an actuator that is mounted on the mobile platform.

Generally speaking a robot has to satisfy conflicting demands. At the one hand it is desirable to have a low mass in order to reduce inertia and improve the speed of operation. On the other hand a robot preferably shows a high stiffness which allows to maintain accuracy when operating with high amplitudes and frequencies. In most cases these requirements conflict with each other and a trade off must occur in the design of the robot between mass and stiffness. A measure of the quality of the design can be found in the so called P/M ratio wherein P stands for payload and M stands for total· mass. The higher this P/M ratio is, the better the design.

A problem of the design known from EP-A-1 870 214 is that the actuator that is mounted on the mobile platform reduces the P/M ratio in that it increases the weight of the mobile platform at the expense of the load that may be supported or handled by the tool or tools that are provided on the platform.

It is one of the objectives of the invention to provide a solution for this problem. A further objective is to provide a design which allows to provide a robot with improved P/M ratio. Still a further objective of the invention is to provide a robot which can represent a viable alternative for the robot or robots that are known from the prior art.

To meet one or more of the abovementioned objectives of the invention and/or to provide a solution to any other objective problem which is not yet described above but may become apparent during processing of this application, the robot of the invention is provided with the features of one or more of the appended claims .

In a first aspect of the invention the robot comprises five legs, wherein each leg connects at its extremities to the base and the platform. This essentially provides the possibility of equipping the robot with five degrees of freedom, wherein the additional degree of freedom as compared to the prior art can be used for operating the tool or tools.

To support meeting this possibility of providing the robot with five degrees of freedom, the platform is embodied with members that are rotationally connected to each other with links, wherein each link is provided at an extremity of one leg.

For ease of operation it is further preferable that the tool or tools are supported by a member and/or a link.

It is possible to provide the mobile platform with only a single tool as in the prior art. Advantageously however, the mobile platform supports two tools occupying a distance between each other that is adjustable by the operation of the actuator.

It is further preferred that the actuator is placed distant from the tool or tools at the base. This effectively reduces the weight of the mobile platform, and improves the earlier mentioned P/M ratio.

Similar to the prior art the robot of the invention also has legs, each leg having a motor drive at the base. Contrary to the prior art however and very cleverly, in the design of the robot of the invention the actuator of the tool or tools is embodied by the joint operation of the motor drives of the legs .

In order to simplify the actuation of the tool or tools, desirably the positions of the motor drives at the base are symmetrical and form an imaginary pentagram. The pentagram accords to the five legs of the robot..

It is further preferable that each of the legs comprises a rotational joint connected to a parallelogram construction comprising the leg's link that connects to the members of the platform at a side distant from the rotational joint.

In its most preferred embodiment the robot of the invention with multiple degrees of freedom comprises five legs linked at a first of their ends to a base, and at a second of their ends opposite to the first ends to a mobile platform, wherein the legs have motor drives that are positioned at the base, which platform carries at least one tool, and wherein the robot further comprises an actuator for operating the tool or tools, which actuator is embodied by the joint operation of the motor drives of the legs.

The invention will hereinafter be further elucidated with reference to a schematic drawing pertaining to a robot according to the invention.

In the drawing:

-figure 1 shows a schematic isometric drawing of a robot according to the invention in a first embodiment;

-figure 2 provides a detailed view of the platform of the robot shown in figure 1; and

-figure 3 provides a detailed view of the platform of a robot according to a second embodiment.

Wherever in the figures the same reference numerals are applied, these numerals refer to the same parts.

With reference first to figure 1 the robot, with multiple degrees of freedom of the invention is denoted with reference 1, comprising multiple legs 2 linked at a first of their ends to a base 3, and at a second of their ends opposite to the first ends to a mobile platform 4. The platform 4 supports in this embodiment two tools 5, 6, and the robot 1 further comprises an actuator for operating the tools 5, 6, the operation of which actuator will become apparent from the following description. The mobile platform 4 is in a detailed view shown in figure 2. In the shown embodiment the two tools 5, 6 may be embodied as vacuum grippers, but also other types of tools are feasible .

As figure 1 clearly shows, the robot 1 comprises five legs 2, wherein each leg 2 connects at its extremities to the base 3 and the platform 4. Each of the legs 2 comprises a rotational joint 10 connected at one end to the base 3, and at the other end to a parallelogram construction 11 that connects to the platform 4. The platform 4 in turn is embodied with members 7 that are rotationally connected to each other with links 8, wherein each link 8 is provided at an extremity of one leg 2. Each leg's link 8 is thus positioned at a side distant from the rotational joint 10 of the concerning leg 2.

It is further shown in figure 1, but more clearly in figure 2 that the tool or tools 5, 6 are supported by either a member 7 or a link 8. It may be preferable that the mobile plat4 form 4 supports two tools 5, 6 as in the shown case, which tools

5, 6 then may occupy a distance between each other that is adjustable by the operation of the robot providing the actuator for said tools 5, 6.

The legs 2 of the robot 1 of the invention each have a motor drive 9 at the base 3, so as to arrange that the actuator of the tool or tools 5, 6 is embodied by the joint operation of these motor drives 9 of the legs 2. The actuator is thus placed distant from the tool or tools 5, 6 and at the base 3 so as to reduce weight on the platform 4. To simplify the operation of the robot 1 it is then desirable that the positions of the motor drives 9 at the base 3 are symmetrical and form an imaginary pentagram.

With reference to figure 3 another embodiment of the platform 4 of the robot of the invention is shown, in which the tool is embodied with gripper fingers 12', 12'' which are actuated by the above described operation in which the motor drives 9 of the legs 2 operate to control the platform 4 in a manner to arrange that the gripper fingers 12', 12'' occupy a preselected distance between each other. Figure 3 also shows that an additional prismatic joint 13 may be placed between the respective gripper fingers 12', 12'' .