【COMP329 LEC4 Locomotion and Kinematics】

Only for the Test 1 which include 4.2 4.3 4.4

Locomotion and Kinematics 运动和运动学

(4.2) Part 2: Wheeled Motion

1. Wheeled Robots

 a. 省略控制双腿需要的计算复杂度

 b. 只限于easy terrain （地形）

 c. 不平坦uneven 不规则irregular 的地形需要很多计算

 d. 轮子的选择根据应用的需要决定

2. Four basic wheel types

3. Features / characteristics

  a. Stability of a vehicle is be guaranteed with 3 wheels . 机器人的稳定性需要三个轮子来保证

 b. Stability is improved by 4 and more wheels

 c. However, such arrangements with more thanthree contact points are hyperstatic 超固定的 and requirea flexible suspension system 灵活的悬挂系统.

 d.  Bigger wheels allow robot to overcome higher obstacles .

 e. Combining actuation 驱动 and steering 转向 on one wheel makesthe design complex and adds additional errors forodometry

 f. 计算速度 v = 2r * w/2 = wr

 g. Four wheels

    1. 高机动性 难控制

 h. Three wheels

    1. Differential drive 差速器驱动器  plus caster 脚轮 or omnidirectional wheel.

         Highly manoeuvrable, but limited to moving forwards/ backwards and rotating 高机动性，但仅限制于向前、向后和转向

 

    2.  Connected drive wheels at rear,  steered wheel at front 前面是转向轮，后面是驱动轮

    3.  Two free wheels in rear, steered drive wheel in front. 后轮是自由的， 前轮是需要操纵的

    

（4.3）Part 3: Two wheeled Vehicles and Manoeuvrability

1. Two Wheels

 Steering wheel at front, drive wheel at back.

  Stability issues, not that common

  Differential drive

  Turning achieved by varying the individual velocity / speed of each wheel

转向通过改变单个轮胎的速度来实现

  Centre of mass above or below axle

 Highly manoeuvrable, but limited to moving forwards/ backwards and rotating 高机动性，但仅限制于向前、向后和转向

 2. Degree of mobility

m ：quantifies the degrees of controllable freedom based on changes to the wheels’ velocity

m = 3 - Nk （where Nk is the number of independent kinematic constraints）

the number of independent fixed or steerable standard wheels 

简而言之，就是独立固定的或者是可操纵的轮胎

例子1：differential drive 什么差速器

例子2：tricycle 三轮车

例子3：bicycle 自行车

3. Mobility vs Steerability

4. Degree of Steerability

5. Degree of Manoeuvrability

机器人可以通过改变车轮的速度（直接移动）和车轮的方向（间接移动）来操纵的整体自由度

两个具有相同 manoeuvrability 特性的机器人并不一定是相等的，但由于可移动性或可操纵性，它们可以以不同的方式进行操纵

6. Non-Holonomic Constraints 非人体工程学约束

（4.4）Part 4 Kinematics of Differential Drives

So far we have looked at different kinds of motion in a qualitative way

• One way to program robots to move is trial and error 试错法 反复实验

1.定义：

A somewhat better way is to establish mathematically how the robot should move, this is kinematics

• Rather kinematics is the business of figuring how a robot will move if it’s motors work in a given way.

运动学的任务是计算如果机器人的马达在特定的方式工作，它将如何移动

固定马达----计算移动

• Inverse-kinematics then tells us how to move the motors to get the robot to do what we want.

然后，逆运动学告诉我们如何移动马达来让机器人去做我们想做的事情

改变马达-----促使移动

没有横向移动条件下的转向

31 / 54 明天在学 学闷了