Robotics Unit basics were discussed here along with types
- 1. U20ECST10 ROBOTICS AND AUTOMATION UNIT II BUILDING BLOCKS OF A ROBOT Types of electric motors - DC, Servo, Stepper; specification, drives for motors - speed & direction control and circuitry, Selection criterion for actuators, direct drives, non-traditional actuators; Sensors for localization, navigation, obstacle avoidance and path planning in known and unknown environments – optical, inertial, thermal, chemical, biosensor, other common sensors; Case study on choice of sensors and actuators for maze solving robot and self driving cars.
- 2. TYPES OF ELECTRIC MOTORS 1.DC Motor A direct current (DC) motor is a type of electric machine that converts electrical energy into mechanical energy. 2.Servo Motor A servomotor is a rotary or linear actuator that allows for precise control of angular or linear position. 3.Stepper Motor A stepper motor, also known as step motor or stepping motor, is an electrical motor that rotates in a series of small angular steps, instead of continuously.
- 3. SPECIFICATIONS OF A MOTOR • Speed • Torque • Current • Power • Voltage • No load speed • No load current • Stall current • Stall torque • Rated Current • Rated Power • Starting Current
- 4. DRIVES OF A MOTOR A drive is the electronic device that controls the electrical energy sent to the motor. The drive feeds electricity into the motor in varying amounts and at varying frequencies, thereby indirectly controlling the motor’s speed and torque. AC Drives: They control the speed of an AC induction motor by adjusting the motor’s input frequency and voltage. DC Drives: DC drives control the speed of DC motors, by varying the input voltage or through pulse width modulation (PWM). Servo Drives: Servo drives control the operation of servo motors, which are high-performance devices often used in applications needing precision control, such as robotics and CNC machinery.
- 5. SPEED AND DIRECTION CONTROL OF A MOTOR • To achieve the speed control an electronic technique called Pulse Width Modulation is used which generates High and Low pulses. These pulses vary the speed in the motor. • For the generation of these pulses a microcontroller is used to set the speed ranges as per the requirement. •We can easily apply this technique in Microcontroller using Aurdino.
- 6. SPEED AND DIRECTION CONTROL OF A MOTOR
- 7. SELECTION CRITERION FOR ACTUATORS • Actuators are mechanical or electromechanical devices that turn energy into motion. • They combine electrical signals with energy sources, ultimately manipulating the physical world around them. • Actuators can open doors, close windows, raise blinds, or move objects to their intended positions. •The following factors to be considered while selecting an actuator. Operating conditions and compliance: Define the conditions of use, safety requirements, and regulatory standards applicable to the actuator. Adhere to specific regulations based on the device’s environment, such as food industry compliance or outdoor usage specifications.
- 8. SELECTION CRITERION FOR ACTUATORS Functional requirements: Analyze the working mechanism required for the device to perform its functions with the desired accuracy. Powering methods and integration : Evaluate the available and suitable power sources for the actuator. Choose options that seamlessly integrate with the device’s power supply without the need for separate power units. Spatial considerations : Consider the actuator’s physical dimensions to ensure a proper fit within the complete device. Control interface: Evaluate the control interface required for effective interaction with the PLC or management system.
- 9. ACTUATOR TYPES Traditional Actuators: Traditional actuators consist of a screw driven by an external motor attached by a coupler, belt, or gearbox to an actuator. The screw is supported by an angular contact ball bearing set. A nut assembly coupled to the thrust rod provides anti-rotation (typically internal), creating linear motion. Integrated Actuators: Integrated actuators have a screw rigidly coupled to and driven by an internal hollow-core servo motor. The screw and a nut travel within the hollow-core rotor of the internal servo motor. A set of angular contact ball bearings supports the screw and servo motor rotor.
- 10. LOCALIZATION SENSOR • Localization is the process to compute the locations of wireless devices in a network. • The main idea in most localization methods is that some deployed nodes with known coordinates transmit beacons with their coordinates in order to help other nodes localize themselves. • It has two types • Beacon Node(ANCHOR) : It’s a node that’s aware of it’s location. • Unknown Nodes: Nodes whose location to be determined with the help of known nodes.
- 11. LOCALIZATION & NAVIGATIONAL SENSORS Used To understand how robots know where they are and how they get to new locations Self-Localisation: • Global Sensors • Odometry • Markers Navigation: • Classical Feature Based • Potential Fields • Behaviour-Based
- 12. GLOBAL SENSORS Satellite Global Position Sensors (GPS) • Outdoor ok – c. 10m accuracy • Military differential GPS < 1m accuracy • Near buildings – too many reflections • Indoors: • Satellite signal not received • Local transmitters usable
- 13. ODOMETRY Odometry: Position measurement by distance travelled • Know current position • Know how much wheels rotate (e.g. current * time) • New position = old position + commanded motion But: • motors inaccurate -> use shaft encoders • wheels slip on surface -> also need some feature tracking ) , , ( y x
- 14. OBSTACLE AVOIDANCE AND PATH PLANNING
- 15. OBSTACLE AVOIDANCE AND PATH PLANNING • The robot is designed to sense any obstacle in its path, avoids and resumes its running. • IR Sensors are used measure the distances with less response times. • Along with IR sensors, reflective sensors may be used for the same purpose. • Microcontroller or Arduino may be used for decision making purpose. • By proper decision making , guiding wheels may be operated to move the robot.
- 16. OPTICAL SENSORS Advantages: • Electromagnetic Immunity • Electrical Isolation • Compact and light • Wide dynamic range • Amenable to multiplexing. • They can be used to measure Temperature , Pressure, Flow , Liquid Level , Displacement ,Vibration, Rotation, Magnetic field, Acceleration, Force , Velocity , strain ……
- 17. OPTICAL SENSORS
- 18. INERTIAL SENSORS • An inertial sensor measures the acceleration and angular velocity of an object along three mutually perpendicular axes. • Example: accelerometer, gyroscope, compass • Inertial sensors based on micro-electromechanical (MEMS) technology have improved its performance over the last decades. However, using MEMS-based inertial sensors the resulting positioning is less accurate than using other technologies like solid state accelerometers or optical gyroscopes.
- 19. THERMAL SENSOR • Temperature sensors work by measuring the voltage across the diode terminals. As the voltage rises, so does the temperature, and then a voltage drop occurs between the transistor terminals and the emitter (in the diode). There are different types of sensors, which are classified according to their connections. •EXAMPLES: THERMOCOUPLE, THERMISTOR
- 20. CHEMICAL SENSOR • Chemical sensors are those devices that detect and convert chemical information (such as concentration, pressure, activity of particles) into an electrical signal to obtain qualitative or quantitative time- and spatial-resolved information about specific chemical components. • Chemical sensors are also efficient in detecting single molecules. Examples include a breathalyzer, carbon monoxide sensor, and electrochemical gas sensor.
- 21. BIO SENSOR • A biosensor is a device that measures biological or chemical reactions by generating signals proportional to the concentration of an analyte in the reaction. •A biosensor typically consists of a bio-receptor (enzyme/ antibody / cell / nucleic acid), transducer component (semi-conducting material / nanomaterial), and electronic system which includes a signal amplifier, processor & display. Transducers and electronics can be combined.