Robotic devices

ES 2 301 643 T3

DESCRIPTION

Robotic devices.

This invention relates to robotic devices.

Preferred embodiments of the invention seek to provide robotic devices that are simple and inexpensive to manufacture, but that nevertheless can operate with high speed and efficiency.

According to one aspect of the present invention, a robotic device is provided comprising:

to. A first track extending between a first and a second end point;

b. A second track, not parallel to the first track, extending between a third and a fourth end point;

c. A first mount mounted for movement along said first track between said first and second end points;

d. A second mount mounted for movement along said second track between said third and fourth end points;

and. Drive means for driving said first and second supports along their respective tracks between their respective end points; Y

F. A robotic arm pivotally mounted on said first bracket at a first location on said arm, and pivotally mounted on said second bracket on a second location on said arm, spaced from said first location, such that movement of said supports along of said tracks causes the movement of said robotic arm.

Such a robotic device is described in document US 5148091.

In the present invention, said robotic arm is mounted in such a way that it can slide relative to one of said first and second supports.

Preferably, said tracks lie in a common plane, and said arm is arranged to move in said common plane or in a plane parallel to said common plane.

Preferably, at least one of said tracks is rectilinear.

Preferably, both tracks are rectilinear.

Preferably, said tracks are mutually orthogonal.

Preferably, said drive means comprise a first drive means to drive said first support and a second drive means, separate from the first drive means, to drive said second support.

Preferably, the or each of said drive means comprises a prime mover mounted on a frame of the device and connected to or to each respective support by means of a drive transmission means.

Preferably, the robotic arm is rectilinear.

Preferably, said first location is at a first end of the robotic arm and said second location is intermediate between the ends of the robotic arm.

Preferably, said arm can slide relative only to the second of said first and second supports.

Preferably, a robotic device like the previous one further comprises clamping means in a third location on said robotic arm.

Preferably, said third location is at a free end of the robotic arm.

Preferably, a robotic device like the previous one further comprises control means for controlling said actuation means.

Preferably, said control means is programmable, to control that said actuating means causes said robotic arm to follow a predetermined trajectory.

ES 2 301 643 T3

Said control means can be programmed to control that said actuation means cause said robotic arm to follow a predetermined trajectory made up of a series of straight lines.

Said control means can be programmed to control said actuation means that said robotic arm follows a predetermined trajectory composed of a series of straight lines and circular arcs.

Preferably, said control means is programmed to control that said actuation means make said robotic arm follow a predetermined trajectory comprising a curve defined by a function of spatial coordinates that is continuous in both its first and second derivatives.

Preferably, said function is continuous in its third derivative.

Preferably said curve comprises a NURB curve (non-uniform rational B-spline).

Preferably, said control means are arranged to control said actuation means in such a way that the time-distance function of movement along said territory comprises a polynomial function having a continuous curve of the first derivative (speed).

Preferably, said control means are arranged to control said actuation means such that the time-distance function of movement along said path comprises a polynomial function having a continuous curve of the second derivative (acceleration).

Preferably, said control means are arranged to control said actuating means such that the time-distance function of movement along said path comprises a polynomial function having a continuous curve of the third derivative (jerk).

In another aspect, the invention provided a method for operating a robotic device according to any of the foregoing aspects of the invention, the method comprising the steps of calculating a path along which the robotic arm must travel, and forcing the robotic arm to move along that path.

Preferably, said method includes the steps of displaying a curve on a screen, and modifying the shape of the curve to define said trajectory.

Preferably, said modification step is carried out by moving with a "click and drag" mouse movement the control points that are separated from said curve and the positions of which affect the shape of said curve.

Preferably, said method includes the step of also displaying on a screen the plane of an area or volume in which said trajectory is to be located, and on said plane said trajectory is superimposed.

For a better understanding of the invention, and to show how the embodiments thereof can be carried out, reference will now be made, by way of example, to the accompanying grammarian drawing, in which:

Figure 1 illustrates an example of a robotic device embodying the present invention; Y

Figure 2 illustrates a control procedure for a robotic device.

The robotic device 1 illustrated in Figure 1 comprises a robotic arm 2 that is pivotally mounted on first and second supports A and C, which in turn are mounted for sliding movement along a first and a second track 3 and 4 respectively.

The first track 3 is rectilinear and extends between the end points Y1 and Y2. The second track 4 is also rectilinear and extends orthogonally with respect to the first track 3, in the same plane, between respective end points X1 and X2. The robotic arm 2 is pivotally mounted on the first bracket A at a first end of the arm 2, and is pivotally mounted on the second bracket C at a point between the ends of the arm 2. The mounting of the arm 2 on the second support C also allows mutual sliding between the arm 2 and the support C. At its free end B, the robotic arm 2 carries a gripper 5, arranged to hold and release parts to be transported by the robotic device 1.

Each of the supports A and C is mounted for sliding movement along its respective track 3 and 4, and is driven by a respective motor 6 and 7, from which movement is transmitted by a respective toothed belt 8 and 9. Motors 6 and 7 are mounted on a frame 10 of robotic device 1. A programmable controller 11 controls the operation of motors 6 and 7.

It can already be seen that, by moving the supports A and C along their respective tracks 3 and 4, the free end B of the robotic arm 2, with the gripper 5, causes it to move along a path P , whose place can be varied by varying the movements of the supports A and C. In many Gothic applications, simply

ES 2 301 643 T3 it is desired to pick up an item from a predetermined location and transfer it to another predetermined location. The illustrated robotic device 1 is particularly suitable for such simple "pick and place" operations, especially when carried out as a two-dimensional operation, where the two tracks 3 and 4 lie in substantially the same plane, together with the robotic arm 2. (which may, from a practical point of view, be in a relatively closely spaced, parallel plane).

The controller 11 can be programmed very simply through Cartesian coordinates to make the supports A and C move sequentially along the x and y axes respectively, such that the free end B of the robotic arm 2 moves in a series of substantially straight lines. If one of the supports A and C is accelerated with respect to the rest in case the other of the supports is being decelerated with respect to the rest, then the straight-line portions of the path P can be joined by curves, for a smoother operation and efficient. The path P can, in general, comprise any formed curve or series of curves (a curve here that includes a straight line).

A significant characteristic of the robotic device 1 shown is that, in contrast to most known robotic devices, the motors 6 and 7 are not placed on the robotic arm 2, but rather are fixed to the frame 10 of the device 1. This means that the robotic arm 2 can have a very small mass, resulting in very high performance in terms of speed and efficiency. For example, in situations where prior robotic devices have been able to cooperate with a maximum speed of approximately 25 cycles per minute, we have found that a robotic device as depicted can operate up to 100 cycles per minute, representing greatly increased speed and efficiency. .

It will be appreciated that a robotic device as shown can be constructed in a simple and inexpensive manner.

Tracks such as 3 and 4 can alternately be placed at a different angle to each other, and need not be rectilinear. For example, one could be straight and the other curved. The tracks and the robot arm do not need to be on the same plane. However, these alternative configurations may involve less simple programming of a controller such as 11.

Motors 6 and 7 as shown can typically be rotary drive motors. Alternatively, linear motors or any other prime mover with suitable drive transmissions can be used. A single prime mover can drive both A and C brackets by suitable drive transmissions.

In a preferred arrangement, the path X, Y (or, theta) of motion P comprises a curve that is continuous in its first and second derivatives. If required, a third (or higher) order derived continuity can also be specified.

The path was shaped from more than one section or segment and can be indicated as "continuous as one piece" along its length. The order of the derivative to satisfy a continuous curve can be specified between each section or segment.

Furthermore, the motion (time-distance) is preferably specified along the path P as a first and / or second derivative (velocity and acceleration) continuous curve. If required, a third derived (jerk) continuity (or greater) can also be specified. The start, end, and maximum colors of all derivatives can also be specified. By specifying the motion along the path P as a polynomial function with the above attributes, one can ensure that the motion is very uniform and has zero acceleration, as well as zero velocity at the two ends of the motion.

A particularly advantageous way of designing the desired path P is by means of a NURB curve (non-uniform rational B-spline). A NURB curve has the desired properties of continuity in its first and second derivatives, and can be easily manipulated without involving in-depth knowledge or use of mathematics. It can provide an efficient and flexible technique that ensures the desired order of the derivative to satisfy a continuous curve, while allowing the curve to conform geometrically.

Splines have been used for many years - boat builders, for example, would use a long, flexible band of material (for example, wood) - a spline - that could be stretched to the desired shape by applying weights on chosen points. Due to the flexible properties of the material, smooth curves would naturally result.

An analogous control procedure can be provided graphically by displaying a line, or spline, on a computer screen, and stretching it into a desired shape using control points that affect the curvature of the line, the line being defined. behavior of the line using a NURB algorithm.

For example, in Figure 2, path P shown by a computer screen 50 has end points 21 and 25, and three intermediate points 22, 23, and 24 through which path P must pass. control

ES 2 301 643 T3 to 36 act on the line 15 of the path P to stretch it into the desired shape. As line 15 is defined (programmed) to have the properties of a NURB, it responds to the movements of control points 31 to 36 to behave accordingly with, for example, continuity in its first and second derivatives, as shown above. previously mentioned.

Control points 31 to 36 can be conveniently moved on the screen by a “click and drag” movement of the mouse, until the path P passes through all desired points 21 to 25. Control points 31 to 36 are they can move in alternative ways. An operator may have the facility to add and remove control points as desired, and / or the option of modifying the "weight" of individual control points or all control points - that is, the degree of the sixth that will have the movement of one or more control points in the shape of line 15.

Figure 2 also shows two obstacles 41 and 42 that the path P has to avoid. Control points 31 36 are adjusted to ensure that obstacles are effectively avoided.

Thus, an operator can easily design a new path P with little or no computer programming requirement. A ground plane (or vertical plane) is displayed on the computer screen 50 by means of a CAD (Computer Aided Design) program, and line 15 with control points 31 to 36 (or as desired) are superimposed on the ground plane. Control points 31 through 36 are then manipulated to shape line 15 to adopt a desired curve shape, between defined end points, passing through defined intermediate points, and / or avoid defined obstacles.

As an alternative to manipulating control points 31 through 36, an operator can specify the end and intermediate points 21 through 25, along with any obstacles such as 41 and 42, and the shape of the NURB curve for line 15 it can be interpolated from those given points, using a NURB algorithm.

Although the above examples of embodiments of the invention are given in two dimensions, it can be appreciated that the principles can easily be adapted to three dimensions. For example, the embodiment of Figure 1 can be adapted by adding orthogonal tracks to those shown.

Although the curved shape of line 15 can be conveniently described in NURB form, which provides a very compact mathematical way of describing the shape of the curve, it can alternatively be described using other polynomial forms.

The operator can also define points of zero velocity and past time at either end or intermediate points, from which a polynomial function of motion can be derived with a minimum transit time (maximum average velocity), but with desirable attributes of curves. continuous in their first and second (and optionally third) derivatives.

The advantage of using such a technique is that the movement can be very smooth and very fast between two points (start and end). It can also self-optimize between endpoints, using NURB control points simply to guide the path over any obstacles in between.

Thus, a user can specify the shape of the path P in two or three dimensions using geometric "control points" that allow the user to interactively visually shape the curve while maintaining the continuity described above, or for the curve to interpolate. a user-defined series of points in two or three dimensions.

Using a graphical display, it is easy for the operator to define a movement that critiques obstacles. Movement can be fast and smooth without the operator having to specify how it is done.

As used herein, the verb "understand" has its normal dictionary meaning, to indicate a non-exclusive inclusion. That is, the use of the word "comprises" (or any of its derivatives) to include one or more characteristics, does not exclude the possibility of including other characteristics as well.