Method of energizing a stepping motor

• US 4,590,412 A
• Filed: 09/11/1984
• Issued: 05/20/1986
• Est. Priority Date: 09/16/1983
• Status: Expired due to Term

• Current Assignee: Omega S.A. (The Swatch Group AG)
• Original Assignee: Omega S.A. (The Swatch Group AG)
• Inventors: Xuan, Mai T., Mokdad, Mohamed
• Primary Examiner(s): Shoop, Jr., William M.
• Assistant Examiner(s): BERGMANN, SAUL
• Application Number:
  US06/649,338
• Time in Patent Office: 616 Days
• Field of Search: 318/696, 318/685, 368/66, 368/157
• US Class Current: 318/696
• CPC Class Codes: G04C 3/143 Means to reduce power consumption by reducing pulse width or amplitude and related problems, e.g. detection of unwanted or missing step

Abstract

A method of controlling a stepping motor comprises supplying the motor with a predetermined quantity of energy E_io from whence there will result an automatic adaptation of the width of the motor drive pulse to the voltage U_o at the motor terminals and the resistance R_i of the energy source. At the moment when the internal energy E_i (t) supplied to the motor, as defined by the integral over a time period of the product of U_o -RI and the current I_t circulating in the motor winding, becomes equal to E_io the drive pulse is cut off (R is the resistance of the motor winding). The circuit for practicing the method according to the invention includes means for measuring the voltage U_o and the energizing current I(t), means for obtaining the difference U_o -RI, a multiplier for forming the product (U_o -RI)I(t) and an integrator the output of which provides a voltage proportional to the internal energy E_i (t).

Claims

1. A method of controlling the application of motor drive pulses having varying widths from an energy source having a changing internal resistance R_i to a stepping motor, said method comprising the steps of:

determining an energy threshold E_io to be supplied to the motor by a pulse for which stepping is assured in all cases of normally occurring loads;

continually measuring the instantaneous voltage U_o across the motor winding terminals and the instantaneous current I(t) circulating in said winding during a pulse supplied by said energy source, the values of said instantaneous voltage U_o and instantaneous current I(t) being dependent on the internal resistance R_i of said energy source;

continually calculating the difference U_o -RI where R represents the winding resistance during said pulse;

continually forming the product (U_o -RI) I(t) during said pulse;

continually integrating said product over a time period t during said pulse whereby the value of the integral represents the energy E_i (t) supplied to the motor;

continually comparing the measured value E_i (t) during said pulse to the predetermined threshold value E_io ; and

,

cutting off the energy supply when E_i (t)=E_io to form the end of said pulse whereby the width of a motor drive pulse varies as the voltage U_o and the resistance R_i of the energy source vary to provide a predetermined quantity of energy equal to said energy threshold E_io to the motor winding.

2. A method as set forth in claim 1 wherein the product (U_o -RI) I(t) is integrated between two time limits, a first for which t=0 corresponding to the instant of application of the motor drive pulse and a second for which t=T_i max , T_i max representing the maximum motor drive pulse width in a situation where the energy supplied to the motor is not sufficient to reach the predetermined energy.

3. A control circuit for controlling the application of motor drive pulses having varying widths from an energy source having a changing internal resistance R_i to a stepping motor, said control circuit comprising:

first means for generating a signal representing an energy threshold E_io to be supplied to the motor by a pulse for which stepping is assured in all cases of normally occurring loads;

second means for continuously measuring the instantaneous voltage U_o across the motor winding terminals and the instantaneous current I(t) circulating in said winding during a pulse supplied by said energy source, the values of said instantaneous voltage U_o and current I(t) being dependent on the internal resistance R_i of said energy source;

third means responsive to said second means for continuously calculating the difference U_o -RI where R represents the winding resistance during said pulse;

multiplier means responsive to said second means and said third means for continuously forming the product (U_o -RI) I(t) during said pulse;

integrating means responsive to said multiplier means for continuously integrating said product over a time period t during said pulse whereby the value of the integral represents the energy E_i (t) supplied to the motor; and

,

comparing means responsive to said first means and said integrating means for continuously comparing the measured value E_i (t) during said pulse to the predetermined threshold value E_io ;

said comparing means including further means for cutting off the energy supply when E_i (t)=E_io to form the end of said pulse, whereby the width of a motor drive pulse varies as the voltage U_o and the resistance R_i of the energy source vary to provide a predetermined quantity of energy equal to said energy threshold E_io to said motor.