17.3 Motion control and robotics
5 min read•august 7, 2024
Motion control and robotics are crucial components of industrial control embedded systems. These technologies enable precise movement and automation in manufacturing, enhancing efficiency and productivity. From servo motors to stepper motors, motion controllers play a vital role in coordinating complex movements.
Robot , programming, and industrial robotics applications further expand the capabilities of embedded systems. Understanding these concepts is essential for designing and implementing effective control systems in modern industrial environments. Safety considerations are paramount to ensure smooth human-robot collaboration.
Motor Types and Control
Servo Motors
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- Servo motors are rotary or linear actuators that provide precise control over angular or linear position, velocity, and acceleration
- Consist of a motor coupled to a sensor for position feedback and a relatively sophisticated controller
- Commonly used in robotics, CNC machinery, and automated manufacturing
- Can be classified as AC or DC servo motors based on their power supply
- Advantages include high precision, fast response, and ability to handle varying loads
Stepper Motors
- Stepper motors are brushless DC electric motors that divide a full rotation into a number of equal steps
- Enable precise positioning and speed control without the need for a closed-loop feedback system
- Consist of a rotor with permanent magnets and a stator with multiple windings
- Move in discrete steps when electrical pulses are applied to the windings in a specific sequence
- Commonly used in 3D printers, CNC machines, and other applications requiring precise positioning
Motion Controllers
- Motion controllers are devices that generate and transmit control signals to drive servo or stepper motors
- Responsible for executing motion commands and providing precise control over position, velocity, and acceleration
- Can be stand-alone units or integrated into a larger control system (PLC or industrial computer)
- Typically include features such as trajectory generation, interpolation, and error compensation
- Modern motion controllers often support multiple axes of motion and can synchronize the movement of multiple motors
Robot Kinematics and Programming
Robot Kinematics
- Robot kinematics is the study of the motion of robots, particularly the relationship between the joint parameters and the position and orientation of the
- determines the position and orientation of the end effector given the joint angles or displacements
- determines the joint angles or displacements required to achieve a desired end effector position and orientation
- Kinematics is crucial for robot motion planning, control, and simulation
- Examples include determining the workspace of a robot arm or calculating the joint angles needed to reach a specific point
Robot Programming
- Robot programming involves creating instructions for a robot to perform specific tasks
- Can be done using various methods, such as teach pendants, offline programming software, or high-level programming languages
- Teach pendant programming involves manually guiding the robot through the desired motions and recording the positions and actions
- Offline programming allows creating and simulating robot programs on a computer before transferring them to the actual robot
- High-level programming languages (Python or C++) enable more complex and flexible robot control and integration with other systems
Path Planning
- is the process of determining a collision-free path for a robot to follow from a start point to a goal point
- Involves considering the robot's kinematics, workspace constraints, and obstacles in the environment
- Common path planning algorithms include A*, , and
- Path planning can be done offline (before the robot starts moving) or online (continuously updating the path based on sensor data)
- Examples include planning a safe path for a to navigate through a warehouse or determining the optimal trajectory for a robot arm to assemble a product
Industrial Robotics
Industrial Robot Types
- Industrial robots are automated, programmable machines designed to perform various tasks in manufacturing and production environments
- Common types include articulated robots (6 or more degrees of freedom), SCARA robots (4 degrees of freedom), Cartesian robots (linear motion along X, Y, and Z axes), and delta robots (parallel arm design for high-speed pick-and-place operations)
- Each robot type has specific advantages and is suited for different applications based on factors such as workspace, payload capacity, speed, and precision
- Examples include using articulated robots for welding and painting, SCARA robots for assembly tasks, and delta robots for packaging and sorting
End Effectors
- End effectors are devices attached to the end of a robot arm to interact with the environment and perform specific tasks
- Common types include grippers (mechanical, vacuum, or magnetic), welding torches, painting nozzles, and custom-designed tools
- The choice of end effector depends on the application, material properties, and required force or precision
- End effectors often incorporate sensors (force/torque, proximity, or vision) to provide feedback and enable adaptive control
- Examples include using a vacuum to pick up and place electronic components or a welding torch end effector for automotive manufacturing
Machine Vision
- involves using cameras and image processing algorithms to enable robots to perceive and interpret their environment
- Enables robots to detect, identify, and locate objects, inspect product quality, and guide their actions based on visual information
- Common machine vision tasks include object recognition, pose estimation, and visual servoing (using visual feedback to control robot motion)
- Requires appropriate lighting, optics, and image processing software to extract relevant features and make decisions
- Examples include using machine vision for quality control inspection, bin picking, and robot guidance in assembly tasks
Safety Systems in Robotics
- Safety is a critical concern in industrial robotics, as robots can pose risks to human workers and cause damage to equipment
- are designed to prevent accidents, detect potential hazards, and mitigate the consequences of failures
- Common safety features include emergency stop buttons, light curtains, safety-rated sensors, and collision detection and avoidance systems
- Risk assessment and safety standards (ISO 10218 and ANSI/RIA R15.06) provide guidelines for the design, integration, and operation of industrial robots
- Examples of safety measures include using light curtains to create a safety perimeter around a robot work cell or implementing force limiting to reduce the risk of injury during human-robot collaboration
Key Terms to Review (34)
A* algorithm: The a* algorithm is a widely used pathfinding and graph traversal method that finds the shortest path from a start node to a goal node in a weighted graph. It combines features of Dijkstra's algorithm and Greedy Best-First Search by using a cost function that accounts for both the cost to reach the node and an estimate of the cost to reach the goal, making it efficient for applications like motion control and robotics.
Actuator: An actuator is a device that converts energy into motion, enabling the control of a mechanism or system. In the realm of motion control and robotics, actuators are crucial components that facilitate precise movement by converting electrical, hydraulic, or pneumatic energy into mechanical movement. These devices play a significant role in ensuring that robotic systems can perform tasks accurately and efficiently, interacting with their environment effectively.
Articulated robot: An articulated robot is a type of robotic arm that consists of joints and links, allowing it to perform a wide range of motions similar to a human arm. This flexibility makes articulated robots highly suitable for various tasks in automation, such as assembly, welding, and painting. Their design typically features multiple rotational joints, which enable them to achieve complex movements and orientations in three-dimensional space.
Automated guided vehicle (AGV): An automated guided vehicle (AGV) is a mobile robot that follows predetermined paths to transport materials or products within a facility without human intervention. These vehicles utilize various technologies like lasers, magnets, or vision systems to navigate and operate safely in environments such as warehouses, factories, and distribution centers. AGVs enhance efficiency by reducing labor costs and minimizing errors in material handling processes.
CAN Bus: CAN Bus, or Controller Area Network Bus, is a robust vehicle bus standard designed for communication among microcontrollers and devices without a host computer. This protocol is widely used in motion control and robotics to facilitate real-time data exchange between various components, ensuring reliable and efficient operation in complex systems.
Cartesian Robot: A Cartesian robot is a type of robotic arm that operates on three linear axes (X, Y, and Z) using a rectangular coordinate system. This robot moves in straight lines and is often used in industrial settings for tasks like pick-and-place operations, CNC machining, and assembly due to its precision and simplicity. Its structure typically consists of three main components: a base, an end effector, and a moving arm that can extend and retract along the axes.
Closed-loop control: Closed-loop control is a system that automatically adjusts its output based on feedback from the process being controlled. This feedback helps maintain desired performance by continuously comparing the actual output to a setpoint and making necessary adjustments. The ability to respond dynamically to changes or disturbances makes closed-loop systems robust and effective for applications requiring precision.
Computer vision: Computer vision is a field of artificial intelligence that enables machines to interpret and process visual information from the world, similar to the way humans do. This technology allows systems to understand images and videos by analyzing visual data, recognizing patterns, and making decisions based on that information. Its applications are vast and crucial in areas such as robotics, autonomous vehicles, and advanced machine learning systems.
Delta Robot: A delta robot is a type of parallel robot that consists of three arms connected to universal joints at the base, allowing for high-speed motion and precise positioning. The unique design enables it to operate efficiently in applications such as pick-and-place tasks, where rapid and accurate movements are essential. Delta robots are known for their lightweight structure, making them suitable for use in industrial automation and robotics.
End effector: An end effector is a device or tool attached to the end of a robotic arm that interacts with the environment to perform specific tasks. It plays a crucial role in robotics, allowing robots to manipulate objects, execute tasks, and carry out operations with precision and efficiency. The design and functionality of end effectors vary widely, ranging from simple grippers to complex tools, enabling diverse applications in fields such as manufacturing, healthcare, and exploration.
Forward kinematics: Forward kinematics is a mathematical process used in robotics and animation to calculate the position and orientation of the end effector of a robotic arm based on given joint parameters. This technique is essential for determining how a robot's movements translate into real-world positions, allowing for precise control and manipulation of objects in various applications.
FPGA: A Field-Programmable Gate Array (FPGA) is an integrated circuit that can be configured by a customer or designer after manufacturing, allowing for the customization of hardware functionality. This flexibility enables the implementation of complex digital circuits and systems, making FPGAs a popular choice in both hardware-software co-design and motion control applications. Their ability to handle parallel processing and real-time operations enhances the efficiency of various designs.
Gripper: A gripper is a type of end-effector used in robotics that allows a robotic arm to grasp, hold, and manipulate objects. It plays a crucial role in various automation tasks by providing the necessary functionality for the robot to interact with its environment. Grippers can be designed in multiple ways, including mechanical, vacuum-based, or soft designs, each suited for specific applications.
Inverse kinematics: Inverse kinematics is a mathematical process used in robotics and animation to determine the joint angles needed for a robotic arm or character to reach a specific position in space. This concept is crucial for motion control, as it allows for precise positioning of end-effectors, such as hands or tools, based on desired coordinates. It directly relates to how robotic systems interpret movement and apply it in real-world applications, helping bridge the gap between intended motion and achievable configurations.
Kalman filter: The Kalman filter is a mathematical algorithm that provides estimates of unknown variables based on a series of measurements observed over time, accounting for noise and inaccuracies. It operates by predicting the future state of a system and then updating this prediction based on new measurements, making it highly effective in motion control and robotics as well as in sensor fusion and data processing.
Kinematics: Kinematics is the branch of physics that deals with the motion of objects without considering the forces that cause this motion. It focuses on parameters such as position, velocity, acceleration, and time, providing a mathematical framework to describe how objects move. In the context of motion control and robotics, kinematics is crucial for determining the trajectories that robotic systems must follow to achieve desired movements accurately and efficiently.
Machine Learning: Machine learning is a subset of artificial intelligence that focuses on the development of algorithms that allow computers to learn from and make predictions based on data. This technology leverages patterns in large datasets to improve decision-making and automate processes, significantly enhancing capabilities in various applications.
Machine vision: Machine vision is a technology that enables machines to interpret and understand visual information from the world, using cameras and image processing software. This capability allows machines to perform tasks such as identifying objects, measuring distances, and guiding robotic movements. It plays a crucial role in automation, helping improve efficiency and accuracy in various applications, especially in motion control and robotics.
Microcontroller: A microcontroller is a compact integrated circuit designed to govern a specific operation in an embedded system. It combines a processor core, memory, and programmable input/output peripherals on a single chip, making it an essential component for controlling devices and systems. Microcontrollers serve as the brain of embedded systems, enabling them to perform tasks such as data processing, control functions, and communication with other hardware components.
Mobile robot: A mobile robot is an autonomous or semi-autonomous device designed to move around in its environment, often equipped with sensors, actuators, and control systems to navigate and perform tasks. These robots are capable of traversing various terrains and environments, utilizing motion control techniques to achieve specific goals, such as exploration, delivery, or assistance in industrial applications.
Motion controller: A motion controller is an electronic device or system that regulates the movement of machines, robots, or other mechanical systems by sending control signals to actuators or motors. These controllers are essential in robotics and automation, enabling precise and coordinated movements necessary for tasks such as assembly, painting, or material handling. By processing input data from sensors and executing control algorithms, motion controllers ensure accurate positioning and speed control of moving parts.
Open-loop control: Open-loop control is a type of control system that operates without feedback. This means that the system makes decisions based solely on the input it receives and executes actions without monitoring the output or the effects of those actions. This method is often simpler and less expensive, but it lacks the ability to adjust or correct its performance based on changes in the environment or system conditions.
Path Planning: Path planning is the process of determining a route for a robot or autonomous system to follow in order to reach a specific destination while avoiding obstacles. This involves analyzing the environment, considering constraints like safety and efficiency, and generating an optimal path that meets all requirements. It plays a crucial role in motion control and robotics by enabling systems to navigate complex spaces effectively.
Pid controller: A PID controller is a control loop feedback mechanism widely used in industrial control systems to maintain a desired output by adjusting input variables. The acronym stands for Proportional, Integral, and Derivative, which are the three fundamental components that determine the controller's response to an error signal. This type of controller is essential in applications where precision and stability are crucial, making it integral in various analog output applications and critical in motion control and robotics.
Probabilistic Roadmaps (PRM): Probabilistic roadmaps (PRM) are a popular motion planning technique used in robotics to navigate complex environments by constructing a graph of feasible paths. This approach involves randomly sampling the configuration space and connecting valid points to create a roadmap that can efficiently guide a robot from a start position to a goal position, even in high-dimensional spaces. PRMs are particularly effective in scenarios where the environment is cluttered or dynamic, making traditional pathfinding methods less practical.
Rapidly-exploring random trees (RRT): Rapidly-exploring random trees (RRT) is a motion planning algorithm that efficiently explores a space by building a tree structure that expands towards randomly selected points. This technique is particularly useful in high-dimensional spaces where traditional methods may struggle, allowing for quick and effective pathfinding in robotic applications. RRT is well-suited for scenarios involving complex obstacles and dynamic environments, making it a go-to approach in motion control and robotics.
Robotic arm: A robotic arm is an automated mechanical device that mimics the motion and functions of a human arm, often used in industrial applications for tasks such as assembly, welding, and material handling. These devices are composed of joints and links that allow for movement in multiple degrees of freedom, making them highly versatile in performing complex tasks with precision and efficiency.
ROS (Robot Operating System): ROS is an open-source framework designed to facilitate the development of robotic software. It provides tools and libraries to help build and manage complex robot systems, allowing developers to integrate hardware and software components seamlessly. With its focus on modularity, communication, and reusability, ROS enables efficient motion control and advanced robotics applications.
Safety Systems: Safety systems are a set of mechanisms and protocols designed to ensure the safe operation of machinery, particularly in environments where human safety is at risk. These systems play a crucial role in motion control and robotics by preventing accidents, ensuring reliability, and protecting both operators and equipment. The integration of safety systems can involve hardware and software components that work together to monitor, detect, and respond to potential hazards in real-time.
SCARA Robot: A SCARA robot, which stands for Selective Compliance Assembly Robot Arm, is a type of industrial robot that is widely used for assembly and manufacturing tasks. This robot features a unique design with two parallel joints allowing horizontal movement while being rigid in the vertical direction, making it especially suitable for tasks that require precision and repeatability. The SCARA robot's configuration allows it to effectively handle various applications such as pick and place operations, assembly, and packaging in a fast and efficient manner.
Sensor feedback: Sensor feedback refers to the information provided by sensors that is used to adjust and control a system's behavior in real-time. This feedback loop is essential for maintaining the desired performance of systems, especially in robotics and motion control, where precise movements and actions are required. By continuously monitoring the environment or system state, sensor feedback enables dynamic adjustments, ensuring that systems can respond effectively to changes and disturbances.
Servo motor: A servo motor is a type of electromechanical device that converts electrical energy into precise mechanical motion, often used for control applications requiring high accuracy and repeatability. It combines a motor with a feedback sensor to enable precise position control, making it ideal for applications in robotics, automation, and motion control systems.
Stepper motor: A stepper motor is a type of electric motor that divides a full rotation into a number of equal steps, allowing for precise control of angular position and speed. This capability makes stepper motors particularly valuable in applications requiring accurate positioning, such as robotics and automation. Their unique design allows them to operate without feedback systems, which can simplify control mechanisms in various devices.
Trajectory planning: Trajectory planning refers to the process of determining a path or trajectory for a moving object, such as a robot or vehicle, to follow in order to achieve a desired outcome. This involves not only defining the spatial path but also specifying the timing and dynamics of the motion, ensuring that the system can move smoothly and efficiently while avoiding obstacles and adhering to constraints.