2机器人运动学

发布于:2023-01-17 ⋅ 阅读:(534) ⋅ 点赞:(0)

2.1 Introduction

Definition: The science of motion which treats motion without regard to the forces that cause it.

Trajectory: Position, Velocity and Acceleration.

Link type: Revolute, Prismatic, Spherical, Screw.


2.2Link Connection

T_{N}=A_{1}*A_{2}*...A_{N} where N=number of links.

(从空间一点到一点需要6自由度,D-H使用4个参数描述)

Denavit-Hartenberg model (D-H model)

\left ( a,d,\theta,\alpha \right )= \left ( link\, length,\,distance\,between\,two\,normals,\,angle\,between\,two\,links, \,link\,twist\right )

旋转的方向一定是Z方向;

 Z放在下一轴的旋转轴;

 X是两个Z轴的common normal(公垂),若common normal平行则任意;

Steps to establish the relationship between two coordinate systems

  1. 绕z轴旋转一个θ角度;
  2. 沿着z轴平移一个d的距离;(1、2可换序)
  3. 沿着新的x轴平移一个a的距离;
  4. 绕着x轴旋转一个α角度 .

 Stanford Arm

Z6轴是安装在球型轴前端的操作器 

Wrist-partitioned;腕臂分割形式,机器人456轴做成球型轴,123旋转/平移轴

 

 机器人标准矩阵

  • In the case of prismatic joint,the origin of the coordinate frame for a prismatic joint is coincident with the next defined link origin.
  • The zero position is defined when d=0 a=0
  • An matirx is reduce to: 

相比较上一个D-H标准矩阵平行轴的D-H矩阵的a恒等于0,α和θ等于0、90、180

注:

旋转轴θ是变化量;

平移轴d是变化量;

平移轴a=0;

初始的坐标系中d=0。

将1的参数带入标准的D=H矩阵

3是平移轴变量只有D;

456球型轴没有d;


2.3 Example for Kinematics

PUMA

 

 


2.4 Frame of Convention

 给定TN求θ1-N


2.5Inverse kinematics

Workspace:

The volume of space which the end-effector of the mainpulator can reach

Dexteruos Workspace:

The volume of space which the robot end-effector of the mainpulator can reach with all orientations

Reach Workspace:

The volume of space which the end-effector of the mainpulator can reach in  at least one direction

For instance

Configuration

A position may be reached with different  configurations

 PUMA Case

For ways to  reach the same wrist position. Another two configurations are present in the minor joints.

 两种逆运动学解法,数值方法与几何方法:

数值方法:

给出三轴机器人的D-H表

用过A1-3相乘与workspace中的一noap相等计算各轴的旋转角度 

解前三轴的解释正能用第4  列的对应相等求解 

 几何法;


2.6 PUMA 560

wrist partition type

primary joins(前三轴):for the positional workespace

minor jiont(球型轴):for the orientation workpace

 Atan2(x,y),用来区分四个象限

 

保持同一种形式

 

 类似欧拉角解法解球形轴

 几何法,切成两个3的问题,在拆成1跟2的问题(不常用)

2.7机器人校正思路-重复定位精度(Repeatability)和精度(Accuracy)

重复定位精度一定比精度高,若果重复定位精度无法满足需求则需要更换机器人。

 校准方法

 

 ……

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