中南大学蔡自兴，谢斌 zxcai, xiebin@mail.csu 2010

机器人学基础第六章机器人传感器 Fundamentals of Robotics Ch.6 Robot Sensors 中南大学蔡自兴，谢斌 zxcai, xiebin@mail.csu.edu.cn 2010 1 Fundamentals of Robotics

Ch.6 Robot Sensors • 6.1 Introduction to Robot Sensors • 6.2 Internal Sensors（内部传感器） • 6.3 External Sensors（外部传感器） • 6.4 Robot Sensor Application Considerations • 6.5 Summary 2 Ch.6 Robot Sensors

6.1 Introduction to Robot Sensors Application of multi-sensors in mobile robot 6.1 Introduction to Robot Sensors

6.1.1 Classification of Robot Sensors • Robot sensors can be divided into two main categories: • Internal state • Detect position and orientation in the coordinate of the robot itself, deal with the detection of variables such as arm joint position, velocity, and acceleration. • External state • Localize the robot to the environment, deal with the detection of variables such range, proximity, and touch. 6.1 Introduction to Robot Sensors

6.1.1 Classification of Robot Sensors • Most needed sensory abilities for robot: • Simple Touch: detect whether the object is there or not. • Compound Touch: detect the size and shape of the object. • Simple Force: detect force along one direction. • CompoundForce: detect forces along multiple directions. • Proximity: non-contact detection of objects. • Simple Vision: detect feature such as holes, lines, and corners. • CompoundVision: recognition of object. 6.1 Introduction to Robot Sensors

6.1 Introduction to Robot Sensors • 6.2 Internal Sensors（内部传感器） • 6.3 External Sensors（外部传感器） • 6.4 Robot Sensor Application Considerations • 6.5 Summary 6 Ch.6 Robot Sensors

6.2 Internal Sensors 6.2.1 Position/Displacement Sensors 位置传感器 • A position sensor is any idea that permits position measurement. It can either be an absolute position sensor or a relative one (displacement sensor). Position sensors can be either linear or angular. • Inductive Non-Contact Position Sensors, String Potentiometer, Linear variable differential transformer (LVDT) , Potentiometer, Capacitive transducer, Hall effect sensor, Proximity sensor (optical), Grating sensor, Rotary encoder (angular), Photodiode array, etc. 6.2 Internal Sensors

6.2.1 Displacement/Position Sensors 1. Linear Potentiometer 线性电位计 Consists of a wirewound resistor (or a thin film resistor), and a sliding contact point. 6.2 Internal Sensors

2. Rotary encoder • A rotary encoder, also called a shaft encoder, is an electro-mechanical device that converts the angular position of a shaft or axle to an analog or digital code, making it an angle transducer. a) 导电塑料型 b) 线圈型 6.2 Internal Sensors

3. Electro-optical Position Sensor • Find the relationship between the distance and the received light volume (shows in Fig. b) in advance, we can measure the displacement x of the light source. a)光电位置传感器 b) 感光量曲线 6.2 Internal Sensors

6.2.2 Angle Sensors 1．Absolute Optical Angle Sensor 光学式绝对型旋转编码器 For example, resolution of a 12 bit encoder is 2-12 = 4096, so we have a resolution of 1 / 4096 (for a round of 360 degrees). 6.2 Internal Sensors

1．Absolute Optical Angle Sensor • Absolute rotary encoders can also be used to detect angular velocity. By comparing current value and stored values, we can obtain the corresponding angular velocity. 6.2 Internal Sensors

2．Relative Angle Sensor光学式增量型旋转编码器 Incremental rotary encoder can only measure relative angle from initial value to current one. Therefore, in order to know the exact current angle value, some other methods (such as the absolute encoder) are needed to identify the initial value of angle. • Counting the number of conversions to calculate relative angle. 6.2 Internal Sensors

2．Relative Angle Sensor • In this approach, no matter the clockwise (CW) rotation, or counter-clockwise (CCW) rotation, output of the sensing light always alternate between H and L, so we can not get the direction of rotation. 6.2 Internal Sensors

2．Relative Angle Sensor • Adding another sensor (B) 1/4 cycle away from sensor A. • Typically, when clockwise (CW) rotation, signal A changes before B, vice versa. 6.2 Internal Sensors

6.2.3 Attitude Sensors 姿态传感器 • Attitude sensors are used to detect the relative relationship between the robot and ground. When the robot is fixed (just as the majority of industrial robot), there is no need to install such sensors. Attitude sensors are essential for mobile robots. • Attitude sensors detect moving changes in position and orientation of the robot that can be used to control the robot implement desired instruction. 6.2 Internal Sensors

1．Gyro Sensor 陀螺仪 • A gyroscope is a device for measuring or maintaining orientation, based on the principles of conservation of angular momentum. Shown right is a rate gyro. 1—电动机2—角度传感器3—转子4一弹簧 6.2 Internal Sensors

2．Other Gyros • gas rate gyroscope 气体速率陀螺仪 • optical gyroscope 光陀螺仪 • piezoelectric vibratory gyroscope压电振动式陀螺 (shown on the right) 6.2 Internal Sensors

6.3 External Sensors 内传感器 6.3.1 Tactile Sensors 触觉传感器 • The prototype of robot tactile sensor is an imitation of human tactile sense of touch functions: • Tactile sense • Pressure sense • Slip sense • Force sense 6.3 External Sensors

1．Touch Sensor 接触觉传感器 Application: Touch sensors are equipped in the palm of the end-effctor in order to grip objects precisely. 6.3 External Sensors

2．Pressure Sensor 压觉传感器 • Robot pressure sensor can detect the pressure and its distribution through an array of piezoelectric elements. (Eg. Springs (弹簧) for mechanical detecting). Applications: By smart control of pressure, end-effector can pick up not only fragile objects as glass cups, but also soft object as tofu and eggs. 6.3 External Sensors

3．Slip Sensor 滑觉传感器 • Slip sensor is used to detect force and displacement in the vertical direction of the pressure. 6.3 External Sensors

4．Force Sensor 力觉传感器 Robot Force sensors can be divided into 3 categories: • Joint force sensor, installed in the joint actuator, measure the output force and torque of the actuator itself, is used to control the feedback of the force. • Wrist force sensor, mounted between the end-effector and the last joint, measure forces and torques on the end-effector for all directions. • Finger force sensor, installed in the robot finger joints, measure the clamping force of an object. 6.3 External Sensors

4．Force Sensor SRI（Stanford Research Institute）研制的六维腕力传感器 Draper实验室研制的六维腕力传感器林纯一研制的腕力传感器 6.3 External Sensors

6.3.2 Distance Sensor 机器人距离传感器 1． Ultrasonic Distance Sensor 超声波距离传感器 Ultrasonic distance sensor is consisting of a transmitter and a receiver, which are both based on piezoelectric effect (压电效应). 6.3 External Sensors

1．Ultrasonic Distance Sensor • Principles of Ultrasonic Ranging- TOF (Time Of Flight ，时间行程法) 超声波测距原理图 6.3 External Sensors

1．Ultrasonic Distance Sensor 6.3 External Sensors

2．Proximity Sensors 接近觉传感器 • A proximity sensor is a sensor able to detect the presence of nearby objects without any physical contact. • A proximity sensor often emits an electromagnetic or electrostatic field, or a beam of electromagnetic radiation (infrared, for instance), and looks for changes in the field or return signal. The object being sensed is often referred to as the proximity sensor's target. 6.3 External Sensors

2．Proximity Sensors • Different proximity sensor targets demand different sensors. For example, a capacitive or photoelectric sensor might be suitable for a plastic target; an inductive proximity sensor requires a metal target. 6.3 External Sensors

6.3.3 Vision Sensors 视觉传感器 • Research have shown that the visual perception of information accounts for 80% of what people perceived from outside world. • Cells of human vision have the magnitude of about 108, is 3000 times to auditory cells(听觉), and over 100 times to the sensory cells of the skin（皮肤触觉）. 6.3 External Sensors

CCD (Charge-Coupled Device) Sensors Charge-coupled device (CCD) is a major technology for digital imaging. Although CCDs are not the only technology to allow for light detection, CCDs are widely used in professional, medical, and scientific applications where high-quality image data is required. 6.3 External Sensors

The impact of change on the image resolution A total of 256 gray scale, from the Figure (a) to (f) followed by resolution of 512 × 512, 256 × 256,128 × 128,64 × 64,32 × 32,16 × 16. 6.3 External Sensors

The impact of change on the image gray Figure (a) to (f) with resolution of 512 × 512, followed by 256, 64,16,8,4, and 2 gray levels. 6.3 External Sensors

The impact of changes in both resolution and grayscale Figure (a) to (f) followed by: 256 × 256,128-level gray scale; 181 × 181,64-level gray scale; 128 × 128,32-level gray scale; 90 × 90,16-level gray scale; 64 × 64,8-level gray scale; 45 × 45,4-level gray scale. 6.3 External Sensors

6.4 Considerations in Robot Sensor Application 机器人传感器应用中考虑的问题 • High precision, good repeatability • Good stability, high reliability • Strong anti-interference ability • Light weight, small size, easy installation • Cheap 6.4 Robot Sensor Application Considerations

6.5 Summary 小结 • 传感机器人是通过各种传感器或传感系统，向机器人提供感觉的装置，如视觉、听觉、触觉、力觉、嗅觉等。这种智能机器人的智能是由传感器提供的。 • 首先阐述机器人传感器的特点与分类，涉及机器人的感觉顺序与策略、机器人传感器的分类以及应用传感器时应考虑的问题。接着分别讨论机器人的内传感器和外传感器。在内传感器部分，研究了位移/位置传感器、速度和加速度传感器及力觉传感器等。

6.5 Summary 小结 • 在外传感器部分，研究了触觉传感器、应力觉传感器、接近度传感器和其他外传感器。 • 最后，举例介绍了一些有代表性的机器人视觉装置，包括机器人眼、视频信号数字变换器和固态视觉装置等。对于各种传感器，着重讨论它们的工作原理，并说明了应用在应该注意的问题。

Thank you For Attention! 41 Fundamentals of Robotics

中南大学蔡自兴，谢斌 zxcai, xiebin@mail.csu 2010