Robot types, actuators, sensors, kinematics, ROS 2 concepts.
Robot Types
| Type | Degrees of Freedom | Use Case | Example |
|---|---|---|---|
| Articulated arm | 4–7 DoF | Assembly, welding, pick-and-place | KUKA KR6, ABB IRB 120 |
| SCARA | 3–4 DoF | Fast horizontal assembly, dispensing | Epson T6 |
| Delta / Parallel | 3 DoF | Ultra-fast pick-and-place in food/pharma | ABB FlexPicker |
| Cartesian / Gantry | 3–4 DoF (linear) | Large workspace, heavy loads, 3D printing | CNC routers, large printers |
| Collaborative (Cobot) | 6–7 DoF | Human-robot collaboration, safe contact | UR5, Franka Emika |
| Mobile (AGV/AMR) | Navigation DoF | Warehouse logistics, last-mile delivery | Boston Dynamics Spot, MiR |
| Humanoid | 20–30+ DoF | Research, service, bipedal locomotion | Atlas, Optimus (Tesla) |
| Soft robot | Continuous deformation | Medical, grasping delicate objects | Festo Bionic Cobot |
Actuators
| Type | Principle | Torque/Force | Speed | Back-drivable |
|---|---|---|---|---|
| DC brush motor | Electromagnetic | Low–medium | High | Yes |
| BLDC motor | 3-phase electromagnetic | Medium–high | Very high | Yes |
| Stepper motor | Discrete steps | Low–medium | Low | Limited |
| Servo (hobby) | BLDC + gear + encoder | Medium | Medium | Partial |
| Harmonic drive | Strain wave gear reduction | Very high (100:1+) | Low | Limited |
| Hydraulic | Pressurized fluid | Very high | Medium | No |
| Pneumatic | Compressed air | Medium | Very high | No |
| Linear actuator | Screw/rack/solenoid | Medium–high | Low–medium | Varies |
| Piezoelectric | Crystal deformation | Low (nm steps) | Very high frequency | No |
Sensors
| Sensor | Measures | Output | Common Interface |
|---|---|---|---|
| Encoder (optical/magnetic) | Angular / linear position | Pulses, A/B/Z | Quadrature, SPI |
| IMU (accel + gyro) | Acceleration, angular rate, orientation | 6-axis data | I²C, SPI, UART |
| LiDAR | 3D point cloud (distance by laser TOF) | Point cloud | Ethernet, USB |
| RGBD camera (RealSense, ZED) | Color + depth | Image + depth map | USB3 |
| Force/Torque sensor | 6-axis force and torque | Analog / digital | CAN, EtherCAT |
| Tactile / pressure | Contact force distribution | Array of pressures | SPI, I²C |
| Proximity (ultrasonic/IR) | Distance to obstacle | Analog voltage, digital | GPIO, I²C |
| GPS / GNSS | Global position | NMEA sentences | UART |
Kinematics
| Concept | Description |
|---|---|
| Forward kinematics (FK) | Given joint angles → compute end-effector pose |
| Inverse kinematics (IK) | Given desired pose → compute required joint angles |
| Jacobian matrix | Maps joint velocities to end-effector velocities: ẋ = J·θ̇ |
| DH parameters | Denavit-Hartenberg convention: a, α, d, θ per joint |
| Workspace | Reachable volume; regular vs dexterous workspace |
| Singularity | Configuration where manipulability = 0; Jacobian rank drops |
ROS 2 Key Concepts
| Concept | Description |
|---|---|
| Node | Basic process unit; subscribes/publishes/provides services |
| Topic | Async publish-subscribe communication channel |
| Service | Synchronous request-response between nodes |
| Action | Long-running task with feedback + preemption |
| TF2 (transform library) | Track coordinate frame transformations over time |
| URDF | XML format describing robot kinematics and visuals |
| ros2 launch | Launch multiple nodes from a single file |
| colcon build | Build tool for ROS 2 packages |
