Method for determining the deformation of structural elements of a delta robot

Abstract

The preferred embodiments relate to the field of measuring technology, and can be used to determine in-motion delta robot arm deformation. The method includes the use of a linear encoder, which is mounted on one side of the delta robot arm, and the shaft is attached to the other side of the arm, and the turning shaft is arranged with freedom of movement inside the linear encoder, and the delta robot arm deformation is determined during its motion by displacement of the said shaft inside the encoder relative to its initial position. The use of the invention enables to simplify the process of determining deformations.

Claims

1. A method for determining in-motion only deformations of a delta robot arm, the method comprising: using indications of an encoder linked to the delta robot arm, and wherein a linear encoder is used as the encoder, which is mounted on one side of the delta robot arm, and a shaft is attached to the other side of the delta robot arm, and the shaft is arranged with freedom of movement inside the linear encoder, and the delta robot arm deformation is determined during its motion by displacement of the shaft inside the encoder relative to its initial position.

2. The method of claim 1, wherein a resolution of the deformation is less than 1 mm.

3. The method of claim 2, wherein a maximum acceleration of the delta robot arm is about 10 g, exposing the delta robot arm to a bending force of about 50 N.

4. The method of claim 3, wherein the resolution is about 0.5 mm.

5. The method of claim 1, wherein a number of indications per mm of encoder displacement will be equal to the reciprocal of 1/Delta, wherein Delta is the linear displacement which is dependent on a number of segments of the delta robot arm.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows a schematic representation of a device designed to implement the presented method for determining in-motion only deformations of the structural elements of the delta robot; and

(2) FIG. 2 shows a schematic representation of the robot arm.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(3) The implementation of this method for determining the in-motion only deformation of the delta robot structural elements will be considered using the example of the deformation of the upper and lower arms of the delta robot.

(4) The delta robot is a high-speed piece of equipment that moves using a carriage. Moreover, accelerations on the carriage can reach 15 g, i.e. during the motion of the delta robot, its arms (both upper and lower) are exposed to significant loads which result in their inevitable deformation. In this regard, this deformation needs to be promptly detected, since any existing deformation of the arms affects the pose accuracy, since slightly bent arm changes the geometry of the delta robot, and the position of the carriage will differ from the computed position.

(5) First, for example, a shaft is attached to the upper arm on one side, and a linear encoder is mounted on the other side of the arm. The shaft and the linear encoder are set so that the shaft moves freely inside the linear encoder. In this setting, the encoder measures the shaft shift inside. After the required equipment is mounted on the upper arm of the delta robot, it is set in motion. Further, specifically during the motion the location of the shaft inside the linear encoder is determined. If during the motion the shaft inside the linear encoder moves, the arm is currently bent (deformed). If during the motion the position of the shaft inside the linear encoder remains unchanged, the arm is not currently deformed.

(6) Next, a specific example of the method is given. In this regard, it is obvious to those skilled in the art that this example is given only as one of the embodiments of the proposed method and cannot be considered the only possible embodiment.

(7) Assume that at the maximum acceleration of the robot, the arm is exposed to a bending force of about 50 N (if 3 arms carry a load of 1 kg with an acceleration of 15 g, this is 150 N in total, since there are three arms, it gives 50 N per arm).

(8) Static tests show that exposure to this force can flex the arm up to 5 mm, and the required measurement accuracy or resolution is 0.5 mm.

(9) Next, the encoder resolution is calculated, according to which one (1) encoder mark should be provided for such a linear displacement, which will give a bending of the lever by 0.5 mm.

(10) For this purpose, this linear displacement (designated as Delta) should be calculated.

(11) Assume that the bent arm consists of 2 segments, AB and BD, the length of which is equal to and is half the arm length L (see FIG. 2).

(12) Shaft displacement inside the encoder is the difference between L and AD. Therefore, the length of segment AD should be found.

(13) CD (see FIG. 2) is known, as this is the required bending resolution of 0.5 mm.

(14) According to the Pythagorean theorem:

(15) $BC=\sqrt{B{D}^2-C{D}^2}=\sqrt{{\left(\frac{L}{2}\right)}^2-C{D}^2}$

(16) Next, the length of AD is defined as the hypotenuse of triangle ACD.

(17) $\mathrm{AD}=\sqrt{{\left(\frac{L}{2}+BC\right)}^2+C{D}^2}$

(18) Since all components are known, the displacement of the Delta shaft inside the encoder is determined using the above formula:
Delta=LAD

(19) The sought-for value, the number of marks per mm of encoder displacement, will be equal to the reciprocal of 1/Delta.

(20) All of the above confirms that this invention provides a highly efficient, publicly available method for determining the in-motion only deformation of structural elements of a delta robot, which does not involve the use of complex and expensive equipment to implement it.