2 


2.1 
general 

2.1.1 
KINEMATICS Branch of theoretical mechanics dealing with the geometry of motion, irrespective of the causes that produce the motion. 

2.1.2 
KINEMATIC ANALYSIS Analysis of the kinematic aspects of mechanisms. 

2.2 
Motion (quantities, states) 

2.2.1 
MOTION Changing position of a body relative to a frame of reference. 

2.2.2 
ABSOLUTE MOTION Motion with respect to a fixed frame of reference. 

2.2.3 
RELATIVE MOTION Motion with respect to a moving frame of reference. 

2.2.4 
INVERSE MOTION Motion of a frame of reference relative to a moving body. 

2.2.5 
FRAME MOTION [TRANSPORTATION] Motion of a moving frame of reference. 

2.2.6 
DISPLACEMENT Change of position of a body with respect to a fixed frame of reference. 

2.2.7 
RELATIVE DISPLACEMENT Displacement with respect to a moving frame of reference. 

2.2.8 
ANGULAR DISPLACEMENT Displacement of a rigid body in rotation. 

2.2.9 
VELOCITY Rate of displacement with respect to time. 

2.2.10 
ABSOLUTE VELOCITY Velocity with respect to a fixed frame of reference. 

2.2.11 
RELATIVE VELOCITY Velocity with respect to a moving frame of reference. 

2.2.12 
FRAME [TRANSPORTATION] VELOCITY Absolute velocity of a particular point of a moving frame of reference. 

2.2.13 
ANGULAR VELOCITY Rate of angular displacement with respect to time. 

2.2.14 
ACCELERATION Rate of change of velocity with respect to time. 

2.2.15 
NORMAL ACCELERATION Component of acceleration of a point normal to its velocity. 

2.2.16 
TANGENTIAL ACCELERATION Component of acceleration of a point collinear with its velocity. 

2.2.17 
ABSOLUTE ACCELERATION Rate of change of absolute velocity with respect to time. 

2.2.18 
RELATIVE ACCELERATION Rate of change of relative velocity with respect to time. 

2.2.19 
FRAME [TRANSPORTATION] ACCELERATION Absolute acceleration of a particular point in a moving frame of reference. 

2.2.20 
CENTRIPETAL ACCELERATION Acceleration of a point towards the centre of curvature of its path as it moves along a fixed curve. 

2.2.21 
CORIOLIS ACCELERATION Component of the absolute acceleration of a point due to its velocity relative to a rotating frame of reference: It equals twice the vector product of the angular velocity of the moving frame of reference and the relative velocity of the given moving point. 

2.2.22 
ANGULAR ACCELERATION Rate of change of angular velocity with respect to time. 

2.2.23 
RETARDATION Tangential acceleration of a point with a sense opposite to that of the velocity of the point. 

2.2.24 
JERK 1. Rate of change of acceleration with respect to time. 2. Sudden change of acceleration. 

2.2.25 
TRANSLATION Motion (or component of the motion) of a rigid body in which each straight line rigidly connected with the body remains parallel to its initial direction. 

2.2.26 
RECTILINEAR TRANSLATION Translation in which the paths of points of a rigid body are straight lines. 

2.2.27 
ROTATION Motion (or a component of the motion of) a rigid body in which all its points move on circular arcs centred on the same axis. 

2.2.28 
ANGLE OF ROTATION Angle turned through by any line rigidly connected with a rotating body and perpendicular to the axis of rotation. 

2.2.29 
PRECESSION Rotation of a rigid body about an axis fixed in space when combined with rotation about an axis fixed in the body, the two axes being concurrent. 

2.2.30 
REGULAR PRECESSION Precession with uniform rotations about the moving and fixed axes. 

2.2.31 
NUTATION Motion of a rigid body occurring simultaneously with a precession, when the angle between the axes of rotation and precession varies in time. 

2.2.32 
CENTRAL MOTION Motion in which the direction of acceleration of a point always passes through a fixed point (called the centre of motion). 

2.2.33 
PLANAR [PLANE] MOTION Motion of a rigid body in which its points describe curves located in parallel planes. 

2.2.34 
SPATIAL MOTION Motion of a body in which at least one of its points describes a spatial curve. 

2.2.35 
SCREW MOTION Motion consisting of a rotation combined with a translation that is parallel to the rotation. 

2.2.36 
SPHERICAL MOTION Spatial motion of a body in which all points of the body move on concentric spheres. 

2.2.37 
ROLLING MOTION Relative angular displacement about a common tangent of two bodies in contact. 

2.2.38 
SPIN MOTION Relative angular displacement about the common normal of two bodies in contact. 

2.2.39 
SLIDING MOTION Relative displacement of the contacting points of two bodies in the tangent plane at their point of contact. 

2.2.40 
STARTING REGIME OF A MACHINE Transient motion between rest and a steadystate motion of a machine. 

2.2.41 
STOPPING REGIME OF A MACHINE Transient motion between a steadystate motion of a machine and rest. 

2.2.42 
STEADYSTATE MOTION OF A MACHINE Motion of a machine when its kinetic energy is constant or is a periodic function of time with the frequency of the motion. 

2.2.43 
UNIFORM MOTION Motion with constant velocity. 

2.2.44 
COEFFICIENT OF NONUNIFORMITY OF MOTION Ratio of the difference between the maximum and minimum values of the generalized velocity to its mean value during one period of the steady motion. 

2.2.45 
PERIODIC MOTION Sequence of motion that repeats itself after set intervals of time. 

2.2.46 
PERIOD (OF A MOTION) Shortest interval of time or another independent variable after which a motion repeats itself. 

2.2.47 
APERIODIC MOTION Unidirectional motion towards a position of a equilibrium. 

2.2.48 
SIMPLE HARMONIC MOTION Motion in which displacement varies sinusoidally with time. 

2.2.49 
PHASE ANGLE Instantaneous argument of a simple harmonic function. 

2.2.50 
STEP MOTION Unidirectional motion periodically interrupted by dwells. 

2.2.51 
DWELL State wherein a point or a link has zero or approximately zero velocity for a finite interval of time. 

2.2.52 
INSTANTANEOUS [MOMENTARY] DWELL State wherein a point or a link has zero velocity and acceleration for an infinitesimal interval of time. 

2.2.53 
PILGRIMSTEP MOTION Motion that is unidirectional with periodically recurring reversals. 

2.2.54 
TRANSFER FUNCTION Function describing the dependence of output motion upon input motion. 

2.2.55 
TRANSMISSION RATIO Input speed divided by output speed. 

2.2.56 
GEAR RATIO Transmission ratio for a gear train. 

2.2.57 
DEAD POINT Configuration of a mechanism in which the input cannot be moved without assistance to the motion of another link. 

2.2.58 
LIMIT POSITION Configuration of a mechanism in which the position of a particular link, such as the output, is in some significant respect a maximum or a minimum. 

2.2.59 
LEAD [PITCH] Translational displacement of a screw during one complete revolution. 

2.2.60 
PITCH Length of the arc of the reference circle between two consecutive corresponding profiles. 

2.2.61 
LIFT Linear displacement of a cam follower. 

2.3 
Kinematic geometry 

2.3.1 
PATH [TRAJECTORY] Line that a moving point describes in a given system of reference. 

2.3.2 
AXIS OF ROTATION Straight line in a rotating rigid body whose points have zero displacement either in a finite time interval, or in an infinitesimal time interval, with respect to a frame of reference. 

2.3.3 
INSTANTANEOUS CENTRE (OF VELOCITY) Point in a rigid lamina moving in its own plane where the velocity relative to a frame of reference is zero at the given instant. 

2.3.4 
SCREW AXIS Straight line in rigid body whose points are displaced relative to a frame of reference, either in a finite or an infinitesimal time interval, coaxial with the line itself. 

2.3.5 
INSTANTANEOUS SCREW AXIS Locus of the points in a rigid body in general spatial motion, whose linear velocity is parallel to the angular velocity vector of the body at the given instant. 

2.3.6 
INSTANTANEOUS CENTRE OF ACCELERATION Point in a lamina moving in its own plane where the acceleration is zero at a given instant. 

2.3.7 
CENTRODE Locus of the instantaneous centre of velocity in the relative planar motion of two laminae, described upon either one lamina or the other. 

2.3.8 
FIXED CENTRODE Locus traced on a fixed lamina by the instantaneous centre of velocity of a coplanar moving lamina. 

2.3.9 
MOVING CENTRODE Locus traced on a moving lamina by its instantaneous centre of velocity as the lamina moves in its own plane. 

2.3.10 
CARDAN CIRCLES Circular fixed and moving centrodes, the diameter of one being half that of the other. 

2.3.11 
AXODE Ruled spatial surface generated in a body by the instantaneous screw axis during its motion relative to another body. 

2.3.12 
FIXED AXODE Axode described in a fixed frame of reference. 

2.3.13 
MOVING AXODE Axode described in a frame of reference that is rigidly connected to the moving body. 

2.3.14 
POLE Point in a rigid lamina whose location does not change as a result of a displacement of the lamina in its own plane. 

2.3.15 
CENTRODE TANGENT Common tangent to the centrodes at the instantaneous centre of velocity. 

2.3.16 
POLE VELOCITY Rate of change of the position of instantaneous centre of velocity with respect to time. 

2.3.17 
BRESSE NORMAL CIRCLE Locus of the points in a lamina moving in its own plane that have zero tangential acceleration at a given instant. 

2.3.18 
INFLECTION CIRCLE Locus of those points in a lamina moving in its own plane that are at points of inflection in their paths and so have zero normal acceleration at a given instant. 

2.3.19 
INFLECTION POINT Point in a path or curve where the radius of curvature is infinite. 

2.3.20 
INFLECTION CENTRE Point where the lines of action of the velocity vectors of points on the inflection circle are concurrent. 

2.3.21 
CUBIC OF STATIONARY CURVATURE Locus of points in a lamina moving in its own plane for which the path curvature is stationary at a given instant (a maximum or a minimum) . 

2.3.22 
CENTRING[PIVOT] POINT CURVE Locus of centres of curvature of the paths of points that lie on the cubic of stationary curvature. 

2.3.23 
BALL POINT Intersection between the inflection circle and the cubic of stationary curvature, other than at the instantaneous centre of velocity. 

2.3.24 
COUPLER POINT Point attached to the coupler of a mechanism. 

2.3.25 
COUPLER (POINT) CURVE Trajectory traced by a coupler point. 

2.3.26 
POLE TRIANGLE Triangle formed by the poles defined by the displacement of a rigid lamina through three positions in its own plane. 

2.3.27 
IMAGE [MIRROR] POLE Reflection of a vertex of a pole triangle in the opposite side of the triangle. 

2.3.28 
OPPOSITE POLE Pole for the displacement of a lamina from any one position to another of four positions in its own plane is opposite to the pole for the displacement from one to the other of the remaining two positions. 

2.3.29 
OPPOSITEPOLE QUADRILATERAL Quadrilateral formed by joining two pairs of opposite poles in such a way that opposite poles are not directly connected. 

2.3.30 
CIRCLE POINT Point in a lamina moving in its own plane which for four positions of the lamina lies on a fixed circle. 

2.3.31 
CIRCLEPOINT CURVE Locus of the circle point on the moving lamina. 

2.3.32 
CENTRE POINT Centre of the fixed circle drawn through four positions of a circle point. 

2.3.33 
CENTREPOINT CURVE Locus of the centre point with respect to the fixed frame of reference. 

2.3.34 
BURMESTER POINT Centre of a fixed circle which passes through five separate positions of a point on a rigid lamina moving in its own plane. Note: For any given set of five positions of the lamina the number of Burmester points is zero, two or four. 