Comprehensive Study Notes: Robot Technology, Components, and Anatomy

General Characteristics of Industrial Robots

• Definition and Evolution: Industrial robots represent a logical evolution of automated equipment, merging features of fixed automation and human labor. They are specialized machine tools with high flexibility.

• Nature of Robots: They are mechanical arms or machines, not mechanical people. They are typically bolted to floors, ceilings, walls, or machines and perform repetitive tasks in ordered environments.

• Sensory Capabilities: While many lack sight or touch, the addition of sensory devices allows robots to adapt to work environments and modify actions based on variations. They fill the gap between limited fixed automation and flexible human labor.

• Work Environment Benefits: Robots are immune to fatigue, discomfort, boredom, or harsh conditions (heat, noise, hazards), making them ideal for strenuous, dangerous, dirty, or repetitive work.

• Work Envelope: The set of points representing the maximum extent or reach of the robot hand or tool in all directions.

• Payload: The maximum weight a robot is designed to lift, hold, carry, and position repeatedly with accuracy at a given speed. It is expressed in $\text{pounds}$ or $\text{kilograms}$.

• Velocity: The maximum speed at which the tip of the robot moves at full arm extension, expressed in $\text{inches/second}$ or $\text{millimeters/second}$. It consists of two components:     * Acceleration/Deceleration Rate: The time required to transition from rest to full speed and from full speed to a complete stop.     * Slew Rate: The constant velocity once the robot is at full speed.

• Cycle Time: The time taken to complete one full cycle (picking up an object at a specific height, moving a specific distance, lowering, releasing, and returning to the start).

• Accuracy: The ability of a robot to position the end effector at a specified point in space upon command without having previously attained that position.

• Repeatability: The ability to return consistently to a previously defined and achieved location.

• Resolution: The smallest incremental change in position that a robot can make or its control system can measure.

• Size: Physical size influences capacity and capabilities. Ranges include units as large as gantry cranes to those as small as grains of salt.     * Micromachining: The process used to create grain-sized robots, identical to the process for integrated circuits and computer chips.     * Human-Sized Robots: Some light assembly robots are designed to be human-sized to minimize disruption when replacing a human worker in an existing workspace.

Basic Components of Industrial Robots

All industrial robots share a common family structure consisting of four basic components:

• Manipulator: The robot's mechanical arm, consisting of segments jointed together with axes capable of motion to perform work.

• End Effector: Also known as End-of-Arm-Tooling (EOAT). It is the gripper, tool, or fixture attached to the manipulator that actually performs the specific task.

• Power Supply: Provides and regulates the energy converted to motion by the actuators.

• Controller: The "brain" of the robot that initiates, terminates, and coordinates motions and sequences. It processes inputs and provides outputs to interface with the world.

The Manipulator and Motion Control

• Primary Function: To provide specific motions enabling the tooling to perform work, simulating human arm movement.

• Motion Categories:     * Arm and Body Motions: Shoulder and elbow motions.     * Wrist Motions: Orientation motions.

• Degrees of Freedom (DOF): Each individual joint motion axis equals one degree of freedom. Industrial robots typically have $\text{4-6}$ degrees of freedom.

• Wrist Orientation Axes: The wrist reaches points in space using three specific orientation motions:     * Pitch: Up-and-down motion.     * Yaw: Side-to-side motion.     * Roll: Rotating motion.

• Joints and Axes: Points where a manipulator bends, slides, or rotates are called joints or position axes. Manipulation uses linkages, gears, actuators, and feedback devices.

• World Coordinate System: A fixed location within the manipulator serving as an absolute frame of reference (Position Axes/World Coordinates):     * $x$ axis: In-and-out motion.     * $y$ axis: Side-to-side motion.     * $z$ axis: Up-and-down motion.

• Anatomic Correspondences: Names of manipulator parts match human counterparts: Base, Shoulder, Arm, Elbow, Wrist.

End Effectors (EOAT)

• Tooling Attachment: A robot becomes a production machine only when a tool is attached via the tool-mounting plate (faceplate).

• Types of End Effectors:     * Grippers: Mechanically opened/closed devices for grasping objects.     * Process Tooling: Special attachments for specific tasks (e.g., welding torches, spray guns).

• Common End Effector Devices:     * Materials handling: Grippers, hooks, scoops, electromagnets, vacuum cups, adhesive fingers.     * Painting: Spray guns.     * Welding/Cutting: Attachments for spot welding, arc welding, and arc cutting.     * Machining/Assembly: Drills, nut drivers, burrs, special fixtures.     * Measurement: Dial indicators, depth gauges.

• Tool Center Point (TCP): The origin of the coordinate system at the point of action. When a tool is added to the tool-mounting plate, the origin moves from the center of the faceplate to the tip of the tool.

• Selection Factors: Payload, environment, reliability, and cost.

Power Supply Systems

• Electricity: The most common power source for industrial robots.

• Pneumatic: The second most common source.

• Hydraulic: The least common source. Used for heavy-duty applications (high payload).

• Integrated Systems Example: The Binks Manufacturing Co. robot (model 88-800) uses a combination: hydraulic for the first three axes, electric for the last three axes, and pneumatic for the end effector.     * Speeds of Binks Model 88-800: $\text{60}^{\circ}\text{/s}$ on $\theta1$, $\text{45}^{\circ}\text{/s}$ on $\theta2$, $\text{32}^{\circ}\text{/s}$ on $\theta3$, $\text{90}^{\circ}\text{/s}$ on $\alpha4$ and $\alpha5$, and $\text{150}^{\circ}\text{/s}$ on $\alpha6$.

Mathematical Principles of Actuators and Motors

• Actuators: Devices converting energy into motion (cylinders, solenoids, or motors).

• Fluid Power Pressure: Pneumatic systems typically operate at $\approx 100\,lb/in^2$. Hydraulic systems operate between $1000\,lb/in^2$ and $3000\,lb/in^2$.

• Double-Acting Cylinder Equations:     * Extension Force: $\text{force (lb)} = \text{pressure (psi)} \times \text{piston area (in}^2\text{)}$     * Extension Velocity: $\text{velocity (ft/sec)} = \frac{\text{input flow (ft}^3\text{/sec)}}{\text{piston area (ft}^2\text{)}}$     * Retraction Force: $\text{force (lb)} = \text{pressure (psi)} \times (\text{piston area (in}^2\text{)} - \text{rod area (in}^2\text{)})$     * Retraction Velocity: $\text{velocity (ft/sec)} = \frac{\text{input flow (ft}^3\text{/sec)}}{\text{piston area (ft}^2\text{)} - \text{rod area (ft}^2\text{)}}$     * Horsepower (by velocity): $\text{horsepower} = \frac{\text{piston velocity (ft/sec)} \times \text{force (lb)}}{550}$     * Horsepower (by flow): $\text{horsepower} = \frac{\text{input flow (gpm)} \times \text{pressure (lb/in}^2\text{)}}{1714}$

• Stepper Motors: DC motors rotating in responding to electrical pulses.     * Step Angle: Usually $\text{0.72}^{\circ}$ to $\text{90}^{\circ}$.     * Accuracy: $\text{1\% - 5\%}$ of step angle ($\text{3\%}$ is common).     * Conversion Formulas:         * $\text{Steps/revolution} = \frac{360}{\text{step angle (degrees)}}$         * $\text{rpm} = \frac{60(\text{sps})}{\text{steps/revolution}} = \frac{1}{6}(\text{sps})(\text{step angle})$         * $\text{sps} = \frac{6(\text{rpm})}{\text{step angle}}$     * Limits: Speed up to $5000\,\text{sps}$, torque up to $6.25\,\text{inch-lbs}$.

Controller Classification and Logic

1. Nonservo (Open Loop)

• Nature: Feedback-less, simple, low cost. Relies on mechanical stops (fixed or variable) to control end-points.

• Names: Limited-sequence, pick-and-place, fixed-stops, or "bang-bang" robots.

• Operation: Controller sends a signal to a valve; the actuator moves until it hits a mechanical stop or activates a limit switch, which signals the controller to proceed to the next step.

• Repeatability: High, within $0.010\,\text{in}$ for small units.

• Disadvantages: Lack of speed control, time lost in mechanical changes, requires accurate placement of stops.

2. Servo (Closed Loop)

• Nature: Use servomechanisms to detect and correct errors using feedback (tachometers, resolvers, encoders).

• Logic: Controller compares desired position to actual position; the difference (error signal) is amplified and applied to a servo valve, which opens proportionally to move the actuator until the error is zero.

• Capabilities: Can stop at any point in the work envelope.

3. Servo-Controlled (Closed Loop with Controlled Path)

• Nature: Continuously controlled path/trajectory. Stores hundreds or thousands of points in memory.

• Feedback: Encoders convert position data to electrical signals. Velocity data is computed to ensure stability and smooth motion.

Robot Anatomy: Five Design Configurations

1. Rectangular (Cartesian): Uses three perpendicular slides to construct $x$, $y$, and $z$ axes. Creates a rectangular work envelope.

2. Cylindrical (Post-type): Uses a vertical column with a radial slide. The column rotates. Creates a cylindrical work envelope.

3. Spherical (Polar): Uses a telescoping arm that pivots vertically on a rotating base. Creates a spherical work envelope.

4. Jointed-arm (Articulated or Revolute): Consists of shoulder and elbow joints rotating about horizontal axes (like a human arm). Work envelope is circular from the top and irregular/scalloped from the side.

5. SCARA (Selective Compliance Assembly Robot Arm): A version of the jointed-arm robot where shoulder and elbow joints rotate about vertical axes. Large cylindrical work envelope; provides vertical rigidity.

Evolution of Robot Controllers (Five Generations)

• First Generation (Repeating Robots): Pneumatic pick-and-place with mechanical sequences (revolving drums with cams).

• Second Generation (Hardwired): Programmable via patch boards and signals from limit/proximity switches. Reprogramming required rewiring relay banks.

• Third Generation (PLC): introduced microprocessors for easy reprogramming of sequences, stops, and velocities.

• Fourth Generation (Microcomputer): Uses minicomputers/microcomputers and programming languages (BASIC, C, C++). Allows for artificial intelligence, vision, and tactile sensors.

• Fifth Generation (AI/Sensors): Full Artificial Intelligence, miniaturized sensors, and complex decision-making capabilities. Future potential for artificial biological robots (Sixth generation).

Robot Selection and Safety

• Selection Process: Task requirements must be defined before choosing a robot. Restructuring tasks helps exploit robot capabilities.

• Technical Criteria: Type (Servo/Nonservo), Work Envelope, Payload, Cycle Time, Repeatability, Drive (Electric/Pneumatic/Hydraulic).

• Nontechnical Criteria: Cost/benefit, reliability, service, commonality of equipment, user training, and safety.

• Safety: Humans and robots should not share workspace unless presence/position-detection sensors are used. Physical barriers are the safest approach.

General Characteristics

• Definition and Evolution: Industrial robots represent a logical evolution of automated equipment, merging features of fixed automation and human labor. They are specialized machine tools with high flexibility.

• Nature of Robots: They are mechanical arms or machines, not mechanical people. They are typically bolted to floors, ceilings, walls, or machines and perform repetitive tasks in ordered environments.

• Sensory Capabilities: While many lack sight or touch, the addition of sensory devices allows robots to adapt to work environments and modify actions based on variations. They fill the gap between limited fixed automation and flexible human labor.

• Work Environment Benefits: Robots are immune to fatigue, discomfort, boredom, or harsh conditions (heat, noise, hazards), making them ideal for strenuous, dangerous, dirty, or repetitive work.

• Work Envelope: The set of points representing the maximum extent or reach of the robot hand or tool in all directions.

• Payload: The maximum weight a robot is designed to lift, hold, carry, and position repeatedly with accuracy at a given speed, expressed in $\text{pounds}$ or $\text{kilograms}$.

• Velocity: The maximum speed at which the tip of the robot moves at full arm extension, expressed in $\text{inches/second}$ or $\text{millimeters/second}$, consisting of acceleration/deceleration rate and slew rate.

• Cycle Time: The time taken to complete one full cycle (picking up an object at a specific height, moving a specific distance, lowering, releasing, and returning to the start).

• Accuracy: The ability of a robot to position the end effector at a specified point in space upon command without having previously attained that position.

• Repeatability: The ability to return consistently to a previously defined and achieved location.

• Resolution: The smallest incremental change in position that a robot can make or its control system can measure.

• Size: Physical size influences capacity and capabilities, ranging from units as large as gantry cranes to those as small as grains of salt, including micromachining and human-sized robots.

Basic Components of Industrial Robots

All industrial robots share a common family structure consisting of four basic components:

• Manipulator: The robot's mechanical arm, consisting of segments jointed together with axes capable of motion to perform work.

• End Effector: Also known as End-of-Arm-Tooling (EOAT), it is the gripper, tool, or fixture attached to the manipulator that performs specific tasks.

• Power Supply: Provides and regulates the energy converted to motion by the actuators.

• Controller: The "brain" of the robot that initiates, terminates, and coordinates motions and sequences, processing inputs and providing outputs to interface with the world.

Robot Anatomy

• Primary Function: To provide specific motions enabling the tooling to perform work, simulating human arm movement.

• Motion Categories: Arm and body motions (shoulder and elbow) and wrist motions (orientation).

• Degrees of Freedom (DOF): Each individual joint motion axis equals one degree of freedom; industrial robots typically have $\text{4-6}$ degrees of freedom.

• Wrist Orientation Axes: The wrist reaches points in space using three orientation motions: pitch (up-and-down), yaw (side-to-side), and roll (rotating motion).

• Joints and Axes: Points where a manipulator bends, slides, or rotates are called joints or position axes. Manipulation uses linkages, gears, actuators, and feedback devices.

• World Coordinate System: A fixed location within the manipulator serving as an absolute frame of reference (Position Axes/World Coordinates).

Robot Generations

• First Generation (Repeating Robots): Pneumatic pick-and-place with mechanical sequences (revolving drums with cams).

• Second Generation (Hardwired): Programmable via patch boards and signals from limit/proximity switches; reprogramming required rewiring relay banks.

• Third Generation (PLC): Introduced microprocessors for easy reprogramming of sequences, stops, and velocities.

• Fourth Generation (Microcomputer): Uses minicomputers/microcomputers and programming languages (BASIC, C, C++), allowing for artificial intelligence, vision, and tactile sensors.

• Fifth Generation (AI/Sensors): Full Artificial Intelligence and miniaturized sensors, providing complex decision-making capabilities. Future potential for artificial biological robots (Sixth generation).

Robot Selection and Safety

• Selection Process: Task requirements must be defined before choosing a robot. Restructuring tasks helps exploit robot capabilities.

• Technical Criteria: Type (Servo/Nonservo), Work Envelope, Payload, Cycle Time, Repeatability, Drive (Electric/Pneumatic/Hydraulic).

• Nontechnical Criteria: Cost/benefit, reliability, service, commonality of equipment, user training, and safety.

• Safety: Humans and robots should not share workspace unless presence/position-detection sensors are used. Physical barriers are the safest approach.

Robot Anatomy

• Manipulator: The robot's mechanical arm, consisting of segments jointed together with axes capable of motion to perform work. It simulates human arm movement by providing specific motions necessary for tasks.

• Degrees of Freedom (DOF): Each individual joint motion axis equals one degree of freedom; industrial robots typically have $\text{4-6}$ degrees of freedom. This allows for a range of movements within the workspace.

• Wrist Orientation Axes: The wrist reaches points in space using three specific orientation motions:

  • Pitch: Up-and-down motion.

  • Yaw: Side-to-side motion.

  • Roll: Rotating motion.

• Joints and Axes: Points where a manipulator bends, slides, or rotates are called joints or position axes. This involves linkages, gears, actuators, and feedback devices to enhance movement flexibility.

• World Coordinate System: A fixed location within the manipulator serving as an absolute frame of reference, which includes the Position Axes/World Coordinates for determining location in the workspace.

• End Effector: Also known as End-of-Arm-Tooling (EOAT), this is the gripper, tool, or fixture attached to the manipulator that performs specific tasks, effectively transforming the robot into a production machine.

• Tool Center Point (TCP): The origin of the coordinate system at the point of action of the end effector. When a tool is added, the origin shifts from the center of the faceplate to the tip of the tool, allowing for precise task execution.