Linkages, kinematics, actuator force and mechanism geometry.
MODULE OVERVIEW
Robotics & Mechanisms in practical engineering work.
Robotics and mechanisms turn actuator motion into a controlled end-effector path. Geometry, singularities, inertia, friction, speed and safety envelope all matter alongside a simple force or torque calculation.
CORE PRINCIPLES
What to establish first
Link geometry maps joint motion to end-effector position.
Required joint torque is load force times perpendicular moment arm, plus dynamics.
Workspace and collision limits should be checked before operating a mechanism.
DESIGN CONCEPTS
Terms worth checking
Kinematics
Moment arm
Payload inertia
Common applications: Pick-and-place cells · Linkage design · Actuator selection
KEY RELATIONSHIP
Static joint torque
T = Fr
F — applied load, N
r — perpendicular moment arm, m
T — torque, N·m
Static torque excludes acceleration, gearbox loss, gravity direction changes and safety margins.
Use the relationship with compatible units, then review the result against the stated design conditions.
WORKED EXAMPLE
Known values → substitution → interpretation
Known values
Payload force = 120 N; moment arm = 0.35 m
Method
T = 120 × 0.35
Interpretation
The static torque is 42 N·m before dynamic and transmission allowances.
KEY DESIGN CHECKS
Confirm the conditions behind the number
Define the governing load case, duty cycle and required design life before using a simplified relation.
Use compatible units and material data for the actual condition, temperature and manufacturing state.
Compare the result with strength, stiffness, fatigue, safety, serviceability and applicable-code requirements.
COMMON ENGINEERING MISTAKES
Keep the model within its scope
Applying static joint torque outside the assumptions shown on this page.
Using a nominal condition while a peak, alternating, transient or environmental case governs the design.
Treating a calculated value as a final component selection without checking interfaces, tolerances and the current governing standard.
AVAILABLE CALCULATORS
Select a calculator
Engineering guide resources
This source-aware module explains the governing relationship, design checks and practical application. Use the related resource below or continue to the calculator library for an interactive calculation.
ReferenceJ. J. Craig, Introduction to Robotics: Mechanics and Control; ISO 10218 and ISO/TS 15066 for robot safety context.ScopeRelationships are presented for the assumptions stated on this page and linked tool.Design reviewCheck material condition, loads, environment and the applicable current code.SafetyResults are educational/preliminary and do not certify safety or compliance.
