ESDU 06002:2011

ESDU 06002 provides guidance on the selection of cam laws
suitable for Dwell-Rise-Fall-Dwell (DRFD) and Dwell-Fall-Rise-Dwell
(DFRD) output motions having equal rise and fall periods, including
ones having an intermediate constant-velocity component in both the
rise and fall actions. The Item extends the scope of Item 82006
that deals with the selection of DRD cam laws.

This Item can be used to define DRFD or DFRD motions formed from
either a single cam law or from blended components of suitable cam
law.

The displacement curve for the follower rise is a mirror-image
of that for the fall. The procedure used for blending cam profiles
ensures continuity of follower displacement, velocity and
acceleration with infinte jerk throughout the motion. The approach
of deriving a DRFD motion from a DRD rise succeeded immediately by
a DFD fall is inferior because the follower acceleration of DRD
motions must be zero at both limits of travel to avoid infinite
jerk. Hence these motions would have unnecessarily high
accelerations and be liable to induce vibration. Instead, the DRFD
and DFRD cam laws given in this Item make the output acceleration
an absolute maximum at the cam angle where the follower
displacement equals the lift, co-incident with the reversal of
velocity.

The cam laws to be found in ESDU 06002 generate the equations of
motion for the rise or fall segment of a DRFD motion as continuous
functions and include: Double Harmonic Motion, Triple Harmonic
Motion, 2-4-5 Polynomial, 3-4-5-6 Polynomial and 3-5-6-7-8
Polynomial motions. Additionally, but suitable only for Components
controlling the reversal of velocity at the maximum follower
displacement of blended motion, the Constant-Cosine-Constant
Acceleration Motion is included.

Output motions having asymmetric rise and fall periods are
analysed in companion ESDU 06003 and examples are provided in ESDU
06004. The use of an associated computer program, described in ESDU
06005, is recommended for all calculations including sensitivity
analyses to optimise the motion.