Module 5: AI in Robotics

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Questions and Answers

What is a main limitation of legged robots on flat surfaces?

Legged robots are notoriously slow on flat surfaces.

What distinguishes a dynamically stable robot from a statically stable robot?

A dynamically stable robot can remain upright while moving, whereas a statically stable robot does so without moving its legs.

Name one power actuation mechanism commonly used in robotics.

Electric motors are the most popular actuation mechanism.

What are the three properties of good internal representations for robot perception?

<p>They should contain enough information for decision-making, be structured for efficient updates, and correspond to natural state variables.</p> Signup and view all the answers

What is the role of the Dynamic Bayes network in robotics perception?

<p>It helps compute the new belief state based on current beliefs and new observations.</p> Signup and view all the answers

How do airborne robots typically achieve movement?

<p>Airborne robots use propellers or turbines for propulsion.</p> Signup and view all the answers

What is the primary distinction between active and passive sensors?

<p>Active sensors send energy into the environment and measure its reflection, while passive sensors capture signals generated by other sources.</p> Signup and view all the answers

What is one challenge associated with robot perception?

<p>Robot perception is challenging due to noisy sensors and partially observable environments.</p> Signup and view all the answers

How do range sensors contribute to robotic functionality?

<p>Range sensors, like sonar and laser range finders, measure distances to objects, aiding in navigation and collision avoidance.</p> Signup and view all the answers

What advantage do proprioceptive sensors provide to a robot?

<p>Proprioceptive sensors inform the robot about its internal state, allowing for better control and accuracy of its movements.</p> Signup and view all the answers

What is the primary function of communication in robotic systems?

<p>Communication facilitates wireless control and data transfer.</p> Signup and view all the answers

In what scenarios might Differential GPS be used effectively?

<p>Differential GPS can achieve millimeter accuracy outdoors under ideal conditions, making it useful for precise location tracking.</p> Signup and view all the answers

What role does computer vision play in imaging sensors?

<p>Imaging sensors use computer vision techniques to process and model the environment based on captured images.</p> Signup and view all the answers

Why is it important for robots to integrate prior knowledge of tasks and environments?

<p>Integrating prior knowledge enables robots to learn efficiently and operate safely without making repeated errors.</p> Signup and view all the answers

What type of imaging sensor captures depth information?

<p>Stereo vision sensors capture depth information by using two or more cameras to create a 3D representation of the environment.</p> Signup and view all the answers

What challenges are associated with using multiple active sensors simultaneously?

<p>Using multiple active sensors can lead to increased power consumption and potential interference between the sensors.</p> Signup and view all the answers

What role do force and torque sensors play in robotics?

<p>They measure forces in both translational and rotational directions, allowing robots to handle fragile objects and adapt to unknown shapes and locations.</p> Signup and view all the answers

Define degrees of freedom (DOF) in the context of robotics.

<p>Degrees of freedom are the independent movements possible within a robot's joints or body, with one DOF counted for each independent direction of movement.</p> Signup and view all the answers

How many degrees of freedom does an Autonomous Underwater Vehicle (AUV) have, and what are they?

<p>An AUV has six degrees of freedom: three for its location in space (x, y, z) and three for its angular orientation (yaw, roll, and pitch).</p> Signup and view all the answers

Describe the degrees of freedom of a human arm.

<p>A human arm has six degrees of freedom, primarily due to five revolute joints and one prismatic joint that enables both rotational and sliding motions.</p> Signup and view all the answers

What distinguishes non-holonomic robots from holonomic robots?

<p>Non-holonomic robots have more effective degrees of freedom than controllable degrees of freedom, while holonomic robots have equal effective and controllable DOFs.</p> Signup and view all the answers

Give an example of a mobile robot and its locomotion mechanism.

<p>A military tank is a mobile robot that uses differential drive with two independently actuated wheels.</p> Signup and view all the answers

Explain the significance of the prismatic joint in a robotic arm.

<p>The prismatic joint generates sliding motion, contributing to the arm's overall degrees of freedom and allowing for linear movements.</p> Signup and view all the answers

In the context of a car, describe its effective and controllable degrees of freedom.

<p>A car has three effective degrees of freedom in a three-dimensional space but only two controllable degrees of freedom: moving forward/backward and turning.</p> Signup and view all the answers

What are the primary categories of robots and what differentiates them?

<p>The primary categories of robots are manipulators, mobile robots, and hybrid robots. They differ in their design and function, with manipulators being stationary, mobile robots being able to move, and hybrid robots combining both capabilities.</p> Signup and view all the answers

What role do sensors play in robotic systems?

<p>Sensors in robotic systems allow robots to perceive their environment and measure their own motion. Examples include cameras for visibility and gyroscopes for orientation.</p> Signup and view all the answers

Identify two applications of manipulator robots and explain their significance.

<p>Manipulator robots are used in assisting surgeons and in car manufacturing. Their precision and reliability are vital for tasks that require accuracy and safety.</p> Signup and view all the answers

What challenges do mobile robots face in real-world environments?

<p>Mobile robots face challenges such as being partially observable and dealing with stochastic motion errors like friction and gear slips. These issues complicate their navigation and task execution.</p> Signup and view all the answers

How do hybrid robots differ from manipulators and what is one of their key advantages?

<p>Hybrid robots combine mobility and manipulators, allowing them to operate in more diverse environments. A key advantage is their wider reach compared to anchored manipulators.</p> Signup and view all the answers

What types of environments pose challenges for robots, according to the content?

<p>Robots operate in environments that are partially observable, stochastic, dynamic, and continuous. These characteristics make effective navigation and task completion more difficult.</p> Signup and view all the answers

What is the importance of effectors in robotic systems and list some examples?

<p>Effectors are crucial as they enable robots to manipulate the physical world; examples include legs, wheels, joints, and grippers. They allow robots to perform tasks by exerting forces on their environment.</p> Signup and view all the answers

Give two examples of tasks that mobile robots can perform and discuss their implications.

<p>Mobile robots can deliver food in hospitals and operate unmanned aerial vehicles for surveillance. These applications enhance efficiency in service delivery and data collection.</p> Signup and view all the answers

What is a motion model in the context of robotics?

<p>A motion model describes how a robot's position changes over time based on control inputs such as speed and direction.</p> Signup and view all the answers

What is the purpose of localization in robotics?

<p>Localization determines where objects or the robot itself are located in the environment, essential for physical interaction.</p> Signup and view all the answers

How does the tracking problem differ from global localization?

<p>The tracking problem has the initial pose of the object known with bounded uncertainty, while global localization starts with an unknown position and broad uncertainty.</p> Signup and view all the answers

What role do landmarks play in localization systems?

<p>Landmarks are stable, recognizable features used by robots to determine their position in the environment.</p> Signup and view all the answers

What is represented by the state vector Xt = (xt, yt, θt) in robotics?

<p>The state vector Xt represents the robot's position in Cartesian coordinates (xt, yt) and its heading (θt).</p> Signup and view all the answers

Define the kidnapping problem in localization.

<p>The kidnapping problem involves the unpredictable movement of the object or robot, challenging the robustness of localization algorithms.</p> Signup and view all the answers

What assumptions do sensor models make about the environment?

<p>Sensor models typically assume that sensors detect stable, recognizable features known as landmarks.</p> Signup and view all the answers

What inputs are involved in the motion model for localization?

<p>The motion model for localization involves inputs from translational velocity (vt) and rotational velocity (wt).</p> Signup and view all the answers

How does Gaussian noise affect range measurements in real-world scenarios?

<p>Gaussian noise introduces uncertainty in the range measurements, leading to variations from the actual distance to an obstacle.</p> Signup and view all the answers

What are the main steps involved in the Monte Carlo Localization (MCL) process?

<p>The MCL process includes initialization of particles, sensor update to assign weights, resampling of particles, and iterating the process as new sensor data arrives.</p> Signup and view all the answers

What is the role of the covariance matrix in Kalman Filters?

<p>The covariance matrix tracks uncertainties in the robot's belief and how it correlates with measurements, reflecting the confidence in the estimated state.</p> Signup and view all the answers

In Simultaneous Localization and Mapping (SLAM), what is the challenge faced by a robot in a dynamic environment?

<p>The challenge is to accurately localize itself while simultaneously building a map of an unknown environment that may change over time.</p> Signup and view all the answers

Explain how the Extended Kalman Filter (EKF) is used in SLAM.

<p>The EKF represents the posterior distribution as a Gaussian, maintaining a mean vector for the robot's pose and landmarks, and a covariance matrix for uncertainties.</p> Signup and view all the answers

What is the primary assumption of the Kalman Filter regarding robot motion and measurement?

<p>The Kalman Filter assumes that both robot motion and measurement models are linear and that the belief distribution is Gaussian.</p> Signup and view all the answers

Why is resampling important in Monte Carlo Localization?

<p>Resampling is crucial because it helps to retain particles that are more likely to represent the robot's state while discarding less probable ones.</p> Signup and view all the answers

How does the motion model contribute to the particle filtering process in MCL?

<p>The motion model predicts the new state of the robot as it moves, guiding the distribution of particles based on the robot's movement.</p> Signup and view all the answers

Flashcards

Active sensors

Sensors that send out energy into the environment and measure how this energy is reflected back. They provide more information but have higher power consumption and potential interference when multiple sensors are used.

Passive sensors

Sensors that passively capture signals already present in the environment, such as light or sound waves.

Range Sensors

Sensors that measure distances to objects, providing information about the robot's surroundings.

Imaging Sensors

Sensors that capture images of the environment, enabling the robot to see and analyze its surroundings.

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Proprioceptive Sensors

Sensors that provide information about the robot's own internal state, such as its position, orientation, and joint angles.

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Sonar Sensors

A type of range sensor that emits sound waves and measures the time it takes for the sound to return after bouncing off an object. Used for underwater and near-range collision avoidance.

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Radar

A type of range sensor that uses electromagnetic waves to measure distances. Used for long-range applications like aircraft navigation.

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Laser Range Finders

A type of range sensor that uses a laser beam to measure distances. Provides accurate measurements for both short and long distances.

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Robots

Physical agents that perform tasks by interacting with the physical world. They have effectors (like arms and legs) to manipulate objects and sensors to perceive their environment.

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Effectors

Robot parts responsible for physical interaction, like arms, legs, wheels, and grippers. They exert forces on the environment.

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Sensors

Robot components that allow them to sense their environment, like cameras, ultrasonic sensors, gyroscopes, and accelerometers.

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Manipulator Robots

Robots that are fixed in place, usually used in industrial settings or hospitals. They feature controllable joints for precise movements.

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Mobile Robots

Robots that can move under their own power, such as wheeled robots, walking robots, and drones. They are used for tasks like delivery, transportation, and exploration.

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Hybrid Robots

Robots that combine both manipulation and locomotion, like humanoid robots and prosthetics. They combine the capabilities of manipulators and mobile robots.

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Partially Observable Environments

A real-world challenge for robots where they can't see everything in their surroundings, like objects behind walls or corners.

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Stochastic Environments

A real-world challenge for robots where uncertainties and errors exist in movement, like friction and gear slips. This means that robots need to be robust and adaptable.

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Synchro drive

A locomotion system where all wheels always point in the same direction and move with the same speed.

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Legged Robots

Robots that move using legs, capable of navigating rough terrain. However, they are slower on flat surfaces and mechanically complex.

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Dynamically stable robot

A type of legged robot that can remain upright while hopping without needing to move its legs.

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Airborne Robots

Robots that rely on propellers or turbines for locomotion, like drones and blimps.

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Underwater Robots

Robots that utilize thrusters to move underwater, such as submarines and autonomous underwater vehicles (AUVs).

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Robot Perception

The process by which robots interpret sensor measurements and create internal representations of their environment.

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Properties of Good Internal Representations

Internal representations in robot perception must have enough information for decisions, be efficiently updatable, and correspond to natural variables in the world.

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Dynamic Bayes Network

A model used in robot perception to analyze the relationship between actions, observations, and the state of the environment. It helps in updating the robot's understanding of its environment over time.

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Motion Model

The way a robot's position changes over time based on control inputs like speed and direction.

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Sensor Model

How a robot understands its environment and itself through its sensors.

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Localization

Determining where objects or the robot is in the environment.

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Global Localization Problem

A problem where the robot's initial location is unknown and it needs to figure out where it is.

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Tracking Problem

A problem where the robot's initial location is known, and it needs to keep track of its position over time.

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Kidnapping Problem

A problem where the robot is moved to an unknown location without knowing where it is.

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Landmarks

Stable, recognizable features in the environment used by a robot to figure out its position.

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Robot's State

The robot's orientation and position in the environment, described by its Cartesian coordinates (x, y) and its heading (θ).

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Force and Torque Sensors

Sensors that measure forces in both translational and rotational directions. Used in handling delicate objects and adapting to unknown object shapes.

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Degrees of Freedom (DOF)

The number of independent movements a robot's joint or body can make. Each axis of movement counts as one DOF.

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Degrees of Freedom in a Robot

A robot, like an underwater vehicle (AUV), has six DOFs: three for its position (x, y, z) and three for its orientation (yaw, pitch, roll).

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Non-Holonomic Robot

Robots with more effective DOFs (possible movements) than controllable DOFs (movements the robot can control).

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Holonomic Robot

Robots with equal effective DOFs and controllable DOFs. Easier to control but mechanically complex.

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Differential Drive Robot

A robot with two independently actuated wheels (or tracks) on each side, like a tank. Controls movement direction.

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Mobile Robot: 2 Controllable DOFs

A robot that can move forward or backward and rotate, like a car.

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Range Scanner

This sensor is used to measure the distance to objects and usually provides a vector of range values along multiple beam directions.

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Monte Carlo Localization

This method estimates a robot's location using particles that represent possible robot states. Particles are updated based on the robot's motion and sensor readings.

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Kalman Filter

This filter assumes the robot's belief about its position is a Gaussian distribution and updates the belief using motion and sensor data.

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Simultaneous Localization and Mapping (SLAM)

This challenging problem involves a robot simultaneously figuring out its location and creating a map of an unknown environment.

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Extended Kalman Filter (EKF) for SLAM

This method uses an Extended Kalman Filter to represent the robot's state and map as a Gaussian distribution, tracking uncertainties and correlations between robot pose and landmarks.

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Sensor Update

The process of using sensor data to improve a robot's estimate of its position and orientation. It involves updating the robot's belief about its state based on sensor readings.

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Resampling

This process involves selecting particles with higher weights in Monte Carlo Localization to represent a more accurate estimate of the robot's location.

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Study Notes

Module 5: AI in Robotics

  • Robotics are physical agents manipulating the physical world
  • Robots are equipped with effectors (legs, wheels, joints, grippers) to apply physical forces to the environment
  • Robots use sensors (cameras, ultrasound, gyroscopes, accelerometers) to perceive their environment and their own motion
  • Robots are categorized into manipulators, mobile robots, and hybrid robots

Manipulator Robots

  • Also known as robot arms
  • Anchored to a workplace (e.g., factory lines, space station)
  • Feature controllable joint chains for precise effector placement
  • Common in industries, hospitals, and art creation
  • Applications include assisting surgeons, car manufacturing, and artwork creation

Mobile Robots

  • Move using wheels, legs, or similar mechanisms
  • Applications include delivering food in hospitals, moving containers, driverless cars (e.g., NAVLAB), unmanned aerial vehicles (UAVs), autonomous underwater vehicles (AUVs), and planetary rovers (e.g., Sojourner)

Hybrid Robots

  • Combine mobility with manipulators (e.g., humanoid robots mimicking human torsos)
  • Can apply effectors further afield than anchored manipulators, but their task is harder, and rigidity is limited
  • Examples include humanoid robots, prosthetics, intelligent environments (smart homes with sensors), and multibody systems (swarms of small robots)
  • Advantages include a wider reach
  • Challenges include a lack of stability compared to anchored systems

Challenges in Real-World Robotics

  • Environment: Partially observable, stochastic, dynamic, and continuous. Robots may not see everything (e.g., around corners), and motion errors may occur (e.g., friction, gear slips). Real-world environments operate in real time. Learning is slower and riskier than in simulations.
  • Safety and Efficiency: Robots must integrate prior knowledge of tasks, environments, and their limitations to learn efficiently and operate safely without repeated errors.

Types of Sensors

  • Passive Sensors: Capture signals generated by other sources in the environment (e.g., cameras).
  • Active Sensors: Send energy into the environment and rely on reflected energy to perceive their environment (e.g., lasers, radar). Multiple active sensors can increase power consumption and create interference.
  • Sensor types are further categorized into whether they record distances (sonar), entire images, or robot properties.

Sensor Classifications

  • Range Sensors (Distance Measurement): Including Sonar, Radar, Laser Range Finders.
  • Close-Range Sensors: Tactile sensors (whiskers, bump panels, touch-sensitive skins)
  • GPS: Measures distances to satellites, enabling accurate location outdoors; often less effective indoors or underwater.
  • Imaging Sensors: Cameras used to create images of the environment, including stereo vision for depth perception
  • Proprioceptive Sensors: Provide information about the robot's internal state; including shaft decoders for measuring rotational motion, inertial sensors like gyroscopes for orientation tracking, and force and torque sensors to measure forces and torques.

Effectors

  • Effectors are the means by which robots move and change the shape of their bodies.
  • Designed with the degree of freedom (DOF). Degrees of freedom refer to the independent movements possible within a robot's joints or body.
  • AUV example, six DOF, three translational and three rotational (yaw, roll, pitch)

Motion Model for Robots

  • If a robot moves slowly in a plane, a precise map can be used.
  • Pose is defined by x, y coordinates and heading.
  • State Vector (Xt) = (xt, yt, 0t)

Motion Model for Localization

  • Inputs include translational velocity (vt) and rotational velocity (wt).
  • Deterministic Models predict future position changes given inputs (vt, wt, and At).

Sensor Model

  • Two types of Sensor Models:
    • Stable, recognizable features in the environment, called Landmarks.
    • Using geometry (range, bearing,) to calculate distance to landmark.

Localization Techniques

  • Monte Carlo Localization (MCL): Uses particle filtering to estimate a robot's location
  • Particles representing possible robot states, updated using motion and sensor models
  • Steps
  • Initialization: Particles uniformly distributed
  • Sensor Update: Measurements assigned weights to particles
  • Resampling: Particles are resampled, keeping those with high weights
  • Kalman Filters: Assumes the robot's belief is a Gaussian distribution with mean (μ) and covariance (Σ); Suitable for linear motion and measurement systems

Simultaneous Localization and Mapping (SLAM)

  • SLAM is a problem where a robot must localize itself and create a map of an unknown environment simultaneously.
    • Assumes a fixed environment for simplicity
    • Extended Kalman Filter (EKF) for SLAM
  • Posterior distribution as a Gaussian
  • Mean vector (ut) contains robot pose and landmark locations
  • Covariance matrix (∑t) tracks uncertainties and correlations

Planning to move

  • Point-to-Point Motion: Delivering the robot or its end-effector to a designated target location.
  • Compliant Motion: Robot movement while physically interacting with an obstacle (e.g., screwing a light bulb)
  • Configuration Space: A better space for path planning than original 3D space, defined by location, orientation, joint angles.
  • Path Planning: Finding a path from one configuration to another using continuous spaces.
  • Major families include cell decomposition and skeletonization.

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