More note for this course check: Advanced-Robotics

### 1. 3D State Description in Robotics

#### 1.1. Demo Case Study: 3D Navigation of a Drone in an Urban Environment

• Super Domain: Path & Motion Planning
• Type of Method: State Representation in 3D Space

#### 1.2. Problem Definition and Variables

• Objective: To represent and track the state of a drone for 3D navigation in an urban environment.
• Variables:
• $q$: State vector including position and orientation in 3D space.
• $(x, y, z)$: 3D Cartesian coordinates for position.
• $(\phi, \theta, \psi)$: Roll, pitch, and yaw angles for orientation.
• Environmental variables: Obstacles’ positions, wind conditions, goal location.

#### 1.3. Assumptions

• The drone operates in a three-dimensional space.
• External conditions like wind and air traffic are either known or can be sensed.

#### 1.4. Method Specification and Workflow

1. State Representation: Define $q = [x, y, z, \phi, \theta, \psi]^T$.
2. 3D Environment Mapping: Utilize 3D maps or LIDAR data for environmental representation.
3. Sensor Integration: Use GPS, gyroscopes, accelerometers, and LIDAR for real-time state updates.
4. Advanced State Estimation: Implement algorithms like Extended Kalman Filter or SLAM (Simultaneous Localization and Mapping) for accurate state estimation in 3D.

#### 1.5. Strengths and Limitations

• Strengths:
• Comprehensive representation of the drone’s position and orientation in 3D space.
• Facilitates complex navigation tasks, including obstacle avoidance and route optimization.
• Adaptable to a variety of 3D navigation tasks in different environments.
• Limitations:
• High computational requirements for real-time state estimation and mapping.
• Sensor accuracy and reliability can significantly affect state estimation.
• Complex environmental dynamics can challenge state representation accuracy.

#### 1.6. Common Problems in Application

• Drift in state estimation due to sensor errors, especially in GPS-denied environments.
• Difficulty in mapping and navigating in cluttered or dynamically changing environments.
• Balancing computational load and real-time performance requirements.

#### 1.7. Improvement Recommendations

• Integrate more robust and diverse sensors (e.g., visual odometry) to enhance state estimation.
• Employ machine learning techniques for predictive modeling of environmental dynamics.
• Optimize algorithms for efficient computation, considering the constraints of onboard processing capabilities.

### 2. Euler Angles and Gimbal Lock in Robotics

#### 2.1. Demo Case Study: Orientation Control of a Robotic Camera System

• Super Domain: Kinematics and Control Systems
• Type of Method: Orientation Representation and Control

#### 2.2. Problem Definition and Variables

• Objective: To control the orientation of a robotic camera system using Euler angles while understanding and mitigating the risks of gimbal lock.
• Variables:
• Euler Angles $(\phi, \theta, \psi)$: Roll, pitch, and yaw angles representing the orientation of the camera.
• Gimbal Lock: A condition where two of the three gimbals align, resulting in a loss of one degree of rotational freedom.

#### 2.3. Assumptions

• The camera system operates under a gimbal mechanism allowing three degrees of rotational freedom.
• The motion and orientation of the system can be accurately measured and controlled using Euler angles.

#### 2.4. Method Specification and Workflow

1. Euler Angle Representation: Define orientation using three rotations about principal axes.
• Sequence of rotations (e.g., Z-Y-X) is crucial for defining the orientation.
2. Gimbal Lock Understanding: Recognize that gimbal lock occurs when the pitch angle ($\theta$) is at 90°, aligning two of the three rotation axes.
3. Orientation Control: Implement control algorithms to adjust roll, pitch, and yaw for desired camera orientation.
4. Gimbal Lock Mitigation: Monitor and manage the pitch angle to avoid approaching critical values where gimbal lock can occur.

#### 2.5. Strengths and Limitations

• Strengths:
• Euler angles provide an intuitive way to describe orientation.
• Suitable for applications with limited rotational movement where gimbal lock can be avoided.
• Limitations:
• Gimbal lock leads to a loss of one rotational degree of freedom, making precise control impossible in certain orientations.
• Euler angles can be less intuitive for complex, three-dimensional rotational movements.

#### 2.6. Common Problems in Application

• Unintentionally entering gimbal lock, resulting in control issues.
• Difficulty in visualizing and programming complex rotations using Euler angles.
• Accumulation of numerical and computational errors, especially near gimbal lock configurations.

#### 2.7. Improvement Recommendations

• Implement quaternion-based representation as an alternative to avoid gimbal lock.
• Use advanced control algorithms that can detect and compensate for approaching gimbal lock conditions.
• Educate operators and programmers about the limitations and risks of gimbal lock in systems using Euler angles.

### 3. 3D State Description in Robotics with Quaternion Improvement

#### 3.1. Demo Case Study: Advanced 3D Navigation of an Aerial Robot in Complex Environments

• Super Domain: Path & Motion Planning
• Type of Method: Enhanced State Representation in 3D Space

#### 3.2. Problem Definition and Variables

• Objective: To accurately represent and manage the 3D state of an aerial robot for complex navigation tasks.
• Variables:
• $q$: Enhanced state vector including position and orientation in 3D space.
• $(x, y, z)$: 3D Cartesian coordinates for position.
• Quaternion $(q_w, q_x, q_y, q_z)$: Representing orientation to overcome Euler angle limitations.

#### 3.3. Assumptions

• The robot operates in a dynamic, three-dimensional environment.
• High accuracy in orientation representation is crucial for navigation and task execution.

#### 3.4. Method Specification and Workflow

1. State Representation: Define $q = [x, y, z, q_w, q_x, q_y, q_z]^T$.
2. Quaternion Usage: Replace Euler angles with quaternions to avoid issues like gimbal lock and provide more accurate and stable orientation representation.
3. Sensor Fusion: Integrate IMU data with visual odometry and LIDAR for robust state estimation.
4. Advanced Algorithms: Use state-of-the-art algorithms like Unscented Kalman Filter or SLAM for precise state tracking in 3D space.

#### 3.5. Strengths and Limitations

• Strengths:
• Quaternions provide a more robust and singularity-free representation of orientation in 3D space.
• Enhanced precision in orientation helps in complex maneuvers and accurate navigation.
• Suitable for high-dynamic environments like aerial robotics in urban or natural terrains.
• Limitations:
• Increased complexity in understanding and implementing quaternion mathematics.
• Higher computational demands for real-time quaternion-based state estimation.
• Requires sophisticated sensor fusion techniques to fully leverage quaternion advantages.

#### 3.6. Common Problems in Application

• Complexity in translating quaternion operations into practical control commands.
• Challenges in seamlessly integrating quaternion data with traditional position sensors.
• Ensuring numerical stability and avoiding normalization issues with quaternions.

#### 3.7. Improvement Recommendations

• Integrate machine learning to predict and compensate for environmental dynamics and sensor inaccuracies.
• Develop specialized algorithms for efficient quaternion normalization and operation.
• Utilize hardware acceleration for real-time processing of complex quaternion-based calculations.

### 5. Displacement in Robotics (Translation and Rotation)

#### 5.1. Demo Case Study: Precise Manipulator Movement in Industrial Robotics

• Super Domain: Kinematics
• Type of Method: Geometric and Kinematic Analysis

#### 5.2. Problem Definition and Variables

• Objective: To accurately describe and control the displacement of a robotic manipulator, including both translation and rotation.
• Variables:
• $\mathbf{p}$: Position vector representing translation in Cartesian coordinates $(x, y, z)$.
• Rotation: Represented by Euler angles $(\phi, \theta, \psi)$, rotation matrices, or quaternions.

#### 5.3. Assumptions

• The manipulator operates within a rigid body framework.
• Joint movements are precise and can be accurately measured.

#### 5.4. Method Specification and Workflow

1. Translation: Described by linear displacement along x, y, and z axes.
• Formula: $\Delta \mathbf{p} = \mathbf{p}{final} - \mathbf{p}{initial}$.
2. Rotation:
• Euler Angles: Changes in orientation described by roll ($\phi$), pitch ($\theta$), and yaw ($\psi$).
• Rotation Matrix: $\mathbf{R} = \mathbf{R}_z(\psi) \mathbf{R}_y(\theta) \mathbf{R}_x(\phi)$.
• Quaternion: $q = [q_w, q_x, q_y, q_z]$, providing a singularity-free representation.
3. Homogeneous Transformation Matrix: Combines translation and rotation in a single matrix.
• Formula: $\mathbf{T} = \begin{bmatrix} \mathbf{R} & \mathbf{p} \ \mathbf{0} & 1 \end{bmatrix}$.

#### 5.5. Strengths and Limitations

• Strengths:
• Provides a comprehensive way to describe both position and orientation.
• Suitable for a wide range of robotic applications, including automation and assembly.
• Facilitates the calculation of kinematic chains and motion planning.
• Limitations:
• Complexity in calculations, especially for rotations in 3D space.
• Euler angles can suffer from gimbal lock in certain configurations.
• Precision depends on the accuracy of the measurement systems.

#### 5.6. Common Problems in Application

• Accumulation of numerical errors in successive transformations.
• Complexity in inverse kinematics for determining joint angles from desired end-effector position.
• Difficulty in intuitively understanding and visualizing quaternion-based rotations.

#### 5.7. Improvement Recommendations

• Implement advanced computational tools for handling complex kinematic calculations.
• Utilize quaternions for rotation to avoid gimbal lock and improve computational efficiency.
• Integrate feedback systems for error correction in real-time motion control.

Reference: The University of Edinburgh, Advanced Robotics, course link
Author: YangSier (discover304.top)

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