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Manufacturing Systems > Robotic Systems > Flashcards

Robotic Systems Flashcards

1
Q

2 social & ethical implications of using telerobotics in healthcare

A

Legal liabilities - who to blame when malpractice occurs
Security of data when medical records pass through different hands/across digital platforms

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2
Q

Workspace

A

area containing all the points an end effector can reach

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3
Q

Forward dynamics

A

calculate joint trajectories, velocities & accelerations from known torque/forces from actuators at joints

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4
Q

Inverse dynamics

A

calculate forces/torques from known joint motion

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5
Q

path planning

A

mapping sequence of moves from start to end point for efficient movement & to avoid obstacles (geometry & environment of robot)

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6
Q

Trajectory

A

Specifies velocity, acceleration & timing of movement along planned path (accounts for dynamics & kinematics of robot)

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7
Q

Why include time history of position, velocity & acceleration of a robot? (4 points)

A

Achieve balance between:
- Operational efficiency (optimise velocity & acceleration for quickest & most energy-efficient path while respecting mechanical limits of manipulator)
- Precision (precisely control velocity & acceleration for smooth, repeatable movement)
- Safety (comply with physical & operational constraints e.g. max allowable velocity & acceleration, avoid abrupt movements that would endanger human operators/delicate parts in robot’s environment)
- Maintenance (deviations from norm indicate potential issues > improve lifespan & reliability of robot)

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8
Q

Joint (configuration) space: A&D, application

A

A - Smoother motion (planned path based on joint angles, directly controlling each joint’s movement) > maintains mechanical integrity & reduces wear on robot
D - lack of environmental awareness (less direct control over end-effector’s interaction with environment, doesn’t account for obstacles/specific requirements of task environment) > issues with collision avoidance
- manufacturing & assembly e.g. automotive assembly lines like screw driving/parts insertion (precise repeatable movements, consistent operation of robot’s joints where environmental interaction is minimal & controlled)

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9
Q

Task (Cartesian) space:
A&D, Application

A

A: Direct control of end-effector’s position & orientation (navigate complex paths & interact with objects in the environment) > high precision & specific interactions with objects
D: Complex computations (solve inverse kinematics at each point of trajectory > computation intensive) > slow operation but real-time applications may require rapid responses
- robotic surgery (precise control of surgical instruments’ positions & orientations is crucial to safety & effectively performing procedures on patients) > direct manipulation of end-effector to patient’s anatomy

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10
Q

Robot singularity

A

Reduced mobility, losing a DOF > large joint velocities are needed to cause robot’s end-effector to move at small velocities in cartesian space/robot cannot move any further in a specific direction > wear & tear

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11
Q

When is a robot in a singular condition?

A

Jacobian matrix doesn’t have an inverse (sine theta2 = 0) or determinant = 0

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12
Q

What is the Denavit-Hartenberg approach for and what are the 4 parameters?

A

assign coordinate frames to each joint to determine forward kinematic equations of a manipulator
L6, slide 16-19

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13
Q

What are the 2 assumptions on axes directions for the D-H parameters to exist & have unique values? (Sketch diagram to illustrate)

A

Axis xi perpendicular to axis zi-1
Axis xi intersects axis zi-1
L6 slide 15

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14
Q

Most important type of robot in manufacturing sector in Industry 4.0 & its features

A

Collaborative/commonly robot - works alongside humans
- range sensors (safe mode when humans too close)
- force sensors (halt operation when collision/impact detected)
- more compact & lightweight frame with soft round edges

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15
Q

5 robot configuration types & their major axes (schematic diagram & workspace)

A

Cartesian - PPP (accurate, heavy loads > pick-and-place, painting, rehabilitation after stroked)
Cylindrical - RPP
Spherical - RRP
SCARA (selective compliant articulated robot for assembly) - RRP
Articulated - RRR

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16
Q

Factors that determine workspace of manipulator

A

link lengths, joint types & limits, presence of limiters

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17
Q

4 common end effectors & applications

A
  • Mechanical gripper for objects with uneven surfaces e.g. mugs
  • suction for vacuum seal with flat even surface e.g. papers, glass sheets (control pressure better)
  • screw e.g. insert nail into wall
  • magnet e.g. magnetic objects
18
Q

Specifications of a robot

A
  • DOFs (planar manipulator has 2 translations & 1 rotation)
  • no. of axes determine flexibility (major - arm positions wrist, minor - wrist orients end-effector)
  • Workspace
  • payload weight (max weight while remaining within other specifications)
  • horizontal reach
  • precision (resolution, accuracy, repeatability)
19
Q

What is a robot?

A

Autonomy - makes independent decisions
Has sensors, actuators, control systems

20
Q

Robot concerns

A
  • Bias - based on learning e.g. fail to recognise certain ethnic groups
  • Deception - to vulnerable users through emotional attachment/dependency
  • Employment - displace certain classes of workers (retrain for better paid & less dangerous job)
  • opacity - unjust decisions aren’t open to correction/transparent > GDPR - right to explanation
  • safety - accidents
  • Oversight - difficult to monitor & assess RAS (robots & autonomous systems) behaviour in open environments
  • Privacy - allow stalker to track someone/law enforcement to track criminal
21
Q

Robot principles

A
  • Reflective equilibrium (assess benefits & drawbacks of institutions & judgement of trade off)
  • Situational awareness (can drivers of AVs drive after a period of autonomous driving?)
  • Participatory design for responsible innovation (reduce bias, understand impact on employment/privacy/safety/ practicality of oversight)
22
Q

Purpose of robots

A
  • dangerous environments (chemical spill cleanup, space exploration)
  • boring & repetitive tasks (vehicle painting, part pick & place)
  • high precision/speed (micro-surgery, precision machining)
  • replace/augment human function (artificial limbs, exoskeleton)
23
Q

Mechanical structure

A
  • Arm - mobility, positions end-effector
  • rigid bodies - links connected by joints
  • wrist - at end of arm for angular position control
  • end-effector - at moving end of manipulator to perform required task
24
Q

Types of joints

A

Revolute (rotary)
Prismatic (translational)
Spherical (rotation at all 3 axis)
Screw (rotation & translation at 1 axis)

25
Q

Redundant vs under-actuated manipulator

A

Redundant - extra DOF e.g. spatial manipulator with more than 6 DOFs to perform high dexterity tasks (avoid obstacles)
Under-actuated - fewer actuators than DOFs e.g. robot hand has 1 motor on a finger connected to a thread to have more DOFs

26
Q

How to limit working range?

A

Add limiter/program limits so it doesn’t interfere with other links > understand configuration by drawing workspaces (operating envelopes)

27
Q

Open-loop/serial kinematic chain

A

1/more link connected to only 1 other link
- higher payload (300 kg) (add more joints)
- larger workspace (less movement constraints)
- slower movements
- lower accuracy

28
Q

Closed-loop/parallel kinematic chains

A

Every link in chain connected to at least 2 other links (forming 1/more closed loops)
- lower payload (2 kg)
- fewer DOF
- smaller workspace
- faster movements
- higher accuracy

29
Q

Kinematic modelling

A

study of motion (trajectories, velocities, accelerations) without considering forces & moments responsible for motion
analytical relationship between joint positions & end effector pose

30
Q

Forward kinematics

A

determine end-effector pose from joint variables (joint space to cartesian space)
Use homogeneous transformation matrix

31
Q

Inverse kinematics

A

determine joint variables from desired end-effector pose (cartesian space to joint space)
Equations are generally nonlinear (multiple/infinite solutions, no closed form solution, no solution)

32
Q

Differential kinematics

A

Relationship between joint velocity & end-effector velocity
Jacobian matrix finds the joint velocities required to achieve desired end-effector velocity (need to end-effector to move at constant velocity e.g. spraying paint on car)
x_dot = J*theta_dot

33
Q

Homogeneous transformation matrix

A

single matrix of rotations and/or translations of a rigid body

34
Q

Dynamic modelling

A

study of motion based on forces & torques

35
Q

Solution approaches for inverse kinematics

A
  • geometric (cosine rule)
  • algebraic
    — analytical/closed form (solve set of equations from homogeneous transformation matrix)
    — iterative (numerical iteration toward desired goal position e.g. MatLab) when kinematic structure complex/unusual (no closed form solution)
36
Q

Approaches for dynamic modelling

A

1) Lagrange-Euler (kinetic & potential energies) > L=K-P
2) Newton -Euler (conservation of linear & angular momentum for all links - apply F=ma to each link)

37
Q

Kinetic energy of rotational system

A

1/2*theta_dot^2
*moment of inertia

38
Q

Parallel axis theorem

A

I = I_cm + md^2
moment of inertia with respect to new axis
d is distance between 2 axis

39
Q

Angular velocity

A

v = theta_dot*r

40
Q

Joint (configuration) space scheme

A

1) Define task space waypoints
2) Solve inverse kinematics for each waypoint for each joint
3) Generate trajectory in* joint* space
4) Move joints according to this trajectory
5) Sensors monitor actual joint positions & velocities, correcting any discrepancies

41
Q

Operational (cartesian) space scheme

A

1) Define task space waypoints
2) Generate trajectory from waypoints in task space
3) Solve inverse kinematics at each time step considering any errors provided by sensors

42
Q

Joint space trajectory generation

A
  • initial & final pose of end-effector
  • initial & final velocities
  • use inverse kinematics to calculate joint variables (find coefficients of cubic polynomial)
  • for each joint, calculate smooth function to connect way points in joint space
  • use nth order polynomial for (n+1) constraints

Manufacturing Systems (4 decks)

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