WO2000040378A1

WO2000040378A1 - Slider crank mechanism based robot arm

Info

Publication number: WO2000040378A1
Application number: PCT/TR1999/000012
Authority: WO
Inventors: Kenan Koser
Original assignee: Kenan Koser
Priority date: 1999-01-06
Filing date: 1999-03-15
Publication date: 2000-07-13
Also published as: AU2969799A

Abstract

The slider crank mechanism based robot arm consists of a robot waist (2) rotating with respect to the robot base (1) and a closed kinematic chain planar mechanism which is connected to the robot waist by a revolute joint. The closed kinematic chain planar mechanism is principally constructed as a special design of a centric or eccentric slider (6) crank (4) mechanism. The slider crank (4) mechanism based robot arm (3) has similar structural and topological properties as both spherical and anthropomorphic robot manipulators and can be alternatively transformed from one another.

Description

DESCRIPTION

Slider crank mechanism based robot arm

This invention is related to a robot arm, which is mainly constructed by using slider crank mechanism.

Robot manipulators are commonly employed in the wide range of the tasks such as, transportation, material handling, loading, welding, miling and drilling, material assembling, part sorting, packaging and measuring in manufacturing processes. Industrial manipulators are essentially open kinematic chain arm like devices and are generally composed of ternary links interconnected to each other by revolute and prismatic joints.

Although open kinematic chain robot arms are relatively simple structures, they generally have insufficient mechanical stiffness and exhibite undesired elastic behaviour that degrade the performance of robot under heavy and high speed operation conditions. On the other hand, closed kinematic chain type robot arms are preferable in many industrial applications due to the their high structural stiffness. One of the most powerfύll alternatives providing high structural stiffness is the use of a closed chain mechanism, called parallelogram mechanism, as a robot arm. Recently, many robot manufacturers such as Fanuc, Comau supply this type of commercial closed kinematic chain robot arms. Another possible way to design a closed chain basic robot arm is to locate a planar two degrees of freedom closed chain mechanism on a rotatable platform. Asada's robot arm which is mainly constructed by using a five bar planar linkage and ABB's robot arm which is principally designed by using a four bar planar mechanism are included in this class of robot manipulators.

Although closed kinematic chain robot manipulators are massive structures, they have many ideal features such as high mechanical stiffness, direct drive facility, lower positioning error and power requirements, good force-velocity characteristics. Also, another important criterion related to the performance of a robot arm is the existance of isotropic points within its workspace. A typical and most commonly used open chain robot arm, called anthropomoφhic robot manipulator and its parallelogram version have only inplane isotropic points on a circle for a specific link lenght ratio of lower and upper arms. On contrast, by suitable kinematic synthesis, it is possible to construct a closed kinematic chain robot arm having many number of isotropic points within its reachable workspace.

This invention is concerned with a slider crank mechanism based robot arm having many excellent and superior features of the open and closed kinematic chain robot arms. The slider crank mechanism based robot arm is designed as a special design of planar centric or eccentric slider crank mechanism. Figure 1 illustrates side view drawing of the robot arm of which numbered components are listed below:

(1) Robot base

(2) Robot waist

(3) Arm

(4) Crank

(5) Coupler (6) Slider

(7) Wrist

(8) Lower and upper compensators

(9) End effector

Referring to Figure 1, robot waist(2) is located on the robot base(l) by a revolute joint and can rotate freely around a fixed axis with respect to the robot base(l). Arm(3) is connected by a revolute joint to the robot waist(2). Crank(4) is connected to the arm(3) by a revolute joint. Slider(6) is supported to the arm (3) by a prismatic joint. Coupler(5) is connected by a revolute joint to the crank(4). Slider(6) and coupler(5) are connected to the wrist (7) by revolute joints. Wrist (7) is formed such that it can be temporary or permenantly locked to the coupler(5) or to the slider(6). Lower and upper compensators(8) are attached between crank(4) and coupler(5) ; arm(3) and robot waist(2). An end effector(9) is attached to the final link wrist (7) in an appropriate manner.

The slider crank mechanism based robot arm created by this invention has also many kinematic and structural advantages. The mechanical structure of closed kinematic chain robot arm realized by this invention is considerably simple. It has high structural stiffness and allows an open front workspace. If the robot arm is synthesized properly, it may have two inplane isotropic points for various link lenght combinations of slider crank mechanism and can satisfy various types of prescribed force- velocity characteristics in the regions within its reachable workspace. The fundamental structure of slider crank mechanism based robot arm originally has four degrees of freedom. However, if slider(6) or coupler(5) is locked to the wrist (7), then its degrees of freedom reduce to three and it transforms to a basic robot arm. As a result of this, the robot arm can be employed as both redundant and nonredundant manipulator. This closed kinematic chain basic robot arm also has similar structural properties of both spherical and anthropmorphic robot arms and can be alternatively transformed from one another. The robot arm can be actuated individually from all the movable links; robot waist(2), crank(4), slider(6), coupler(5), wrist (7) and end effector(9). Furthermore, the slider crank mechanism based robot arm allows to locate motors close to the base. This structural versality and driving flexibility of the robot arm offers high performance characteristics and dexterity for many different operational conditions. In general, the slider crank mechanism based robot arm includes much of the excellent and superior features of the conventional open and closed chain robot arms.

Claims

1) A slider crank mechanism based robot arm includes a robot base(l), a robot waist(2) supported by a revolute joint to the robot base(l), an arm (3) connected by a revolute joint to the robot waist(2), a crank(4) connected to the arm by a revolute joint, a slider(6) supported by a prismatic joint to the arm(3), a coupler(5) connected by a revolute joint to the crank (4), a wrist (7) to which coupler (5), slider(6) and end effector(9) are connected by revolute joints.

2) A slider crank mechanism based robot arm according to claim 1 wherein the structure of the robot arm consists of a closed kinematic chain planar mechanism which is formed by a special design of a centric or eccentric slider crank mechanism located on the robot waist(2).

3) A slider crank mechanism based robot arm according to claim 1 wherein the wrist (7) may be locked to the slider(6) or to the coupler(5) temporary or permenantly.

4) A slider crank mechanism based robot arm according to claim 1 wherein all or some group of movable links; robot waist(2), arm(3), crank(4), coupler(5), slider(6), wrist (7) may be actuated individually and independently.

5) A slider crank mechanism based robot arm according to claim 1 wherein the lower and upper compensators(8) are attached between arm(3) and robot waist(2) ; crank (4) and coupler(5).