Download NOTES 2.2: Basics of Mechanics of Robots- important concepts about Friction and more Study notes Robotics in PDF only on Docsity!
D.E.S.H. – Department of Engineering, Sciences and Humanities
FY (AY-20-22-1) – RME – Robot Mechanics and Electronics
Notes 2.2 – Basics of Mechanics of Robots
IMPORTANT CONCEPTS ABOUT FRICTION –
A) Friction always opposes the motion. This opposition is called as Friction Force. Friction is a property of the two surfaces in contact.
Friction force is independent of the area of contact of the two surfaces. Figure 2.1 depicts the schematic diagram for Friction
Figure 2.1 Schematic diagram for Friction
B) Causes of Friction:- 1) Intermolecular force of attraction 2) Irregularities between the two surfaces. Figure 2.2 depicts Causes of Friction
Figure 2.2 Causes of Friction
C) Types of Friction :- Figure 2.3 depicts Types of Friction
Figure 2.3 Types of Friction
Vishwakarma Institute of Technology
D.E.S.H. – Department of Engineering, Sciences
FY (AY-20-22-1)
Notes 2.
D) Important Terminology about Friction at the inclined plane
- Impending motion = body is on the verge of motion.
- Limiting Equilibrium = When body is in Impending motion.
- Angle of Repose = Angle at which the motion just starts because its own weight.
- Limiting Friction (F (^) L) = motion just starts.
- Friction Force will be maximum
- The force required to maintain motion with uniform velocity is less than to set a body into motion (Limiting Static Friction Force = F
- The Limiting Frictional Force (F
- Coefficient of Friction (μ) motion of two surfaces in contact
E) Various Forces Acting on a System
Vishwakarma Institute of Technology
Department of Engineering, Sciences and Humanities
1) – RME – Robot Mechanics and Electronics
Notes 2.2 – Basics of Mechanics of Robots
Important Terminology about Friction at the inclined plane-
body is on the verge of motion.
When body is in Impending motion.
Angle at which the motion just starts because its own weight.
) = It is the maximum friction force developed at the contacts before the
maximum when body is on the verge of Impending Motion.
The force required to maintain motion with uniform velocity is less than into motion (Limiting Static Friction Force = FL )
l Force (FL) is proportional to the Normal Reaction (N
Coefficient of Friction (μ) - It is the ratio of the Limiting Frictional force (F motion of two surfaces in contact to the Normal reaction (NR ) pressing the two surfaces.
Various Forces Acting on a System – Figure 2.4 depicts forces acting
and Humanities
Robot Mechanics and Electronics
Angle at which the motion just starts because its own weight.
It is the maximum friction force developed at the contacts before the
verge of Impending Motion.
The force required to maintain motion with uniform velocity is less than the force required
) is proportional to the Normal Reaction (NR )
Limiting Frictional force (FL) resisting the pressing the two surfaces.
D.E.S.H. – Department of Engineering, Sciences and Humanities
FY (AY-20-22-1) – RME – Robot Mechanics and Electronics
Notes 2.2 – Basics of Mechanics of Robots
Concept of CG:- Figure 2.7 depicts the concept of CG
Figure 2.7 concept of CG
J) Centre of Mass (CM) –
- The centre of mass (C.M.) is a point at which the entire mass of the body can be assumed to be C.G. is a function of the Gravity.
- The C.M. is independent of gravity.
- C.M. = C.G. if density of mass is uniform.
K) Centre of Volume (CV) -
- The centre of volume is defined as the point at which the whole volume of the body can be assumed to be concentrated.
- C.V. = C.G. if density of mass is uniform.
L) Centroid of Line and Area -
- The earth’s attraction has no effect on the lines, curves or geometrical figures having area because they do not possess mass or volume.
- Therefore, the centre of gravity, centre of mass and centre of volume does not apply to lines, curves or such other geometrical figures.
- Centroid applies to two dimensional plane laminas or figures and one dimensional lines, wires, rods etc.
Vishwakarma Institute of Technology
D.E.S.H. – Department of Engineering, Sciences
FY (AY-20-22-1)
Notes 2.
- Centroid of line is defined as the point at which whole length of the line may be assumed to be concentrated
- Centroid of area (plane lamina or figure) is defined as the point, at which of the lamina or figures may be assumed to be concentrated
M) Axis of Symmetry – Axis of Symmetry is the line which divides a body into 2 parts, so that the moments of these parts about the axis of symmetry are equal and opposite. symmetry.
N) Centroid is that imaginary point in the Curve or Area where whole of the Curve or Area can be assumed to be concentrated. It is not necessary that the Centroid should lie on the Curve or insid Centroid of curves and Areas.
Figure 2.
O) Steps to determine Centroid of Lines and Curves
Vishwakarma Institute of Technology
Department of Engineering, Sciences and Humanities
1) – RME – Robot Mechanics and Electronics
Notes 2.2 – Basics of Mechanics of Robots
Centroid of line is defined as the point at which whole length of the line may be assumed
Centroid of area (plane lamina or figure) is defined as the point, at which of the lamina or figures may be assumed to be concentrated
Axis of Symmetry is the line which divides a body into 2 parts, so that the moments of these parts about the axis of symmetry are equal and opposite. Figure 2.8 depicts the Axis of
Figure 2.8 Axis of symmetry.
Centroid is that imaginary point in the Curve or Area where whole of the Curve or Area can be
It is not necessary that the Centroid should lie on the Curve or inside the Area. Figure 2.
Figure 2.9 Centroid of curves and Areas.
Steps to determine Centroid of Lines and Curves – Figure 2.10 To find Centroid of lines and curves
and Humanities
Robot Mechanics and Electronics
Centroid of line is defined as the point at which whole length of the line may be assumed
Centroid of area (plane lamina or figure) is defined as the point, at which the whole area
Axis of Symmetry is the line which divides a body into 2 parts, so that the moments depicts the Axis of
Centroid is that imaginary point in the Curve or Area where whole of the Curve or Area can be
Figure 2.9 depicts the
o find Centroid of lines and curves
D.E.S.H. – Department of Engineering, Sciences and Humanities
FY (AY-20-22-1) – RME – Robot Mechanics and Electronics
Notes 2.2 – Basics of Mechanics of Robots
Figure 2.12 Stepwise solved problem
U) Steps to determine Centroid of Area – Figure 2.12 depicts Steps to determine Centroid of Area
Figure 2.12 Steps to determine Centroid of Area
----------------------------------------------------------------------------------------------------------
