Page 1087 - The Mechatronics Handbook

TABLE 39.1 Failure Modes of Parallel Manipulators and Their Effects
Failure Levels Failure Modes Failure Causes Effects
Components Links Break Overload, fatigue, Reduction in number of branches
impact, material
flaw
Joints Common Joint break Overload, fatigue, Reduction in number of branches
impact, material
flaw
Joint jam Deterioration, Reduction in DOF of corresponding
external branch
interference
Active Actuator failures Depends on Reduction in actuation, DOF if joint
actuator type not back-drivable
Transmission Depends on Reduction in actuation, DOF if joint
failures transmission not back-drivable
type
Sensor failures Depends on sensor Reduction in sensing, actuation,
type maybe DOF
Passive sensed Sensor failures Depends on sensor Reduction in sensing
type
Passive unsensed Common failures Overload, fatigue, Reduction in number of branches;
(break, jam) impact, material reduction in DOF
flaw;
deterioration,
external
interference
Branches Common Break Joint/link break Reduction in number of branches,
maybe actuation and DOF,
interference with other branches
Loss of DOF Joint jam, locked Reduction in DOF of manipulator
active joint,
branch
singularity
Active Loss of actuation Active joint failure Reduction in actuation, maybe DOF
Loss of sensing Sensor failure Reduction in actuation, degradation
to passive branch
Passive Loss of sensing Sensor failure Reduction in sensing, degradation to
sensed passive unsensed branch
Passive Common failures Joint/link break, Reduction in constraint or DOF of
unsensed (break, loss of joint jam, locked manipulator
DOF) active joint,
branch
singularity
Manipulator Loss of DOF Joint jam, branch Insufficient DOF
singularity,
branch
interference
Loss of actuation Active Degradation in force and motion
joint/branch capabilities
failure
Loss of constraint Reduction in Uncontrolled motion of manipulator
number of active
branches
Passive unsensed Uncontrolled motion of manipulator
Uncertainty Instantaneous uncontrolled motion
branch break
configuration of manipulator

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