US 5,659,234 AGranted

Vibration reduction for stepping motor by vector angle and vector length modulation

AssigneeAgfa-Gevaert

InventorMarc Cresens

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Abstract

A method is disclosed for the reduction of vibrations in a system using a stepping motor, driving parts at a constant velocity. On a test rig, the dynamic behaviour of the stepping motor in micro stepping mode is measured by a system comprising a rotation encoder. The measured data are filtered and used to compensate the unwanted speed fluctuations. In a first method, compensation is done by modification of the theoretical current-vector angles of basic micro stepping, while keeping the current-vector length constant. In a second method, first the current-vector angles are optimized, where after the current-vector lengths are optimized to correct the stepping motor for a wide range of speeds and load torques. In both methods, the stepping frequency is constant over all steps and determined by the desired angular speed of the stepping motor.

Claims16

Dependent claims

A method for driving a two phase stepping motor at a desired constant angular speed in micro stepping mode comprising the following steps:

choosing a maximum constant current-value I.sub.0, based upon the characteristics of said stepping motor;
establishing a sequence of M current-value pairs (I.sub.xi, I.sub.yi), current-value I.sub.xi corresponding to the electric intensity I.sub.x of a current in a coil X of said stepping motor and current-value I.sub.yi corresponding to the electric intensity I.sub.y of a current in a coil Y of said stepping motor;
establishing the duration T of a micro step based upon said desired angular speed;
applying repeatedly said sequence wherein each of said current-value pairs (I.sub.xi, I.sub.yi) is applied sequentially and wherein I.sub.x and I.sub.y corresponding to said current-value pair (I.sub.xi,I.sub.yi) are applied simultaneously to said coil X and Y for said duration T of a micro step;
wherein said current-value pairs (I.sub.xi, I.sub.yi) have following properties:
(1) the square root I of the quadratic sum I.sup.2 =I.sup.2.sub.xi +I.sup.2.sub.yi of the current-values I.sub.xi and I.sub.yi of each individual current-value pair has a value substantially equal to said maximum constant current-value I.sub.0 ;
(2) a plurality of current-values I.sub.xi have a value substantially equal to I*cos(360.degree.*i/N+.alpha.), wherein:
I is said square root of said quadratic sum I.sup.2 ;
i is an integer index in the sequence (I.sub.xi,I.sub.yi), ranging from 1 to M;
N is an integer divider of M;
and
.alpha. is an arbitrary constant;
is characterised therein that:
(3) at least one current-value I.sub.xi has a value substantially different from I*cos(360.degree. *i/N+.alpha.).

11 more elements

Dependencies are inferred from the claim text.