Drive system in a geodetic measurement instrument

Patent metadata

Field	Value
Publication number	US-12018942-B2
Application number	US-202016998958-A
Country	US
Kind code	B2
Filing date	Aug 20, 2020
Priority date	Aug 21, 2019
Publication date	Jun 25, 2024
Grant date	Jun 25, 2024

Abstract

A geodetic surveying instrument to move a measurement light beam into a desired measurement direction in space, comprising at least one movement axis which is motorized, providing a positioning of the measurement direction of the geodetic surveying instrument, and an instrument-encoder at the movement axis configured for deriving the measurement direction as a measurement value of the geodetic surveying instrument. The geodetic surveying instrument comprises a transmission link of the movement axis of the geodetic surveying instrument to a motor axis of a stepper motor, which transmission link is configured with a gear reduction and a slipping clutch arrangement, and wherein the stepper motor comprises a rotational motor-encoder on its motor-axis and is driven by a motor controller that provides a field oriented control of phase currents of the stepper motor, which field orientation is derived based on the rotational motor-encoder.

First claim

What is claimed is:

1. A geodetic surveying instrument, configured to move a measurement light beam into a desired measurement direction in space, the geodetic surveying instrument comprising:
at least one movement axis which is motorized for providing a positioning of the measurement direction of the geodetic surveying instrument;
an instrument-encoder at the movement axis configured for deriving the measurement direction as a measurement value of the geodetic surveying instrument; and
a transmission link of the movement axis of the geodetic surveying instrument to a motor axis of a stepper motor,
wherein the transmission link is configured with a gear reduction and a slipping clutch arrangement, and
wherein the stepper motor comprises a rotational motor-encoder on its motor-axis and is driven by a motor controller that provides a field oriented control of phase currents of the stepper motor, which field orientation is derived based on the rotational motor-encoder,
wherein the gear reduction is configured as a worm gear drive or as a planetary gear drive.

2. The geodetic surveying instrument according to claim 1 , wherein the gear reduction is configured as a substantially self-locking transmission.

3. The geodetic surveying instrument according to claim 1 , wherein the instrument-encoder is a high accuracy rotational encoder with a resolution of at least one arc second or below, configured with an evaluation unit comprising a positional error compensation and evaluation unit.

4. The geodetic surveying instrument according to claim 1 , wherein the field oriented control is a cascaded controller comprising:
a field oriented current controller for driving the phase currents of the stepper motor based on current sensors for the phase currents and on the motor-encoder, that is cascaded under a control input from a speed loop controller based on the instrument-encoder of the movement axis, that is cascaded under a control input from a position loop controller based on the instrument-encoder of the movement axis,
wherein a position loop controller is provided with a desired trajectory of movement from a geodetic measurement controller of the geodetic surveying instrument.

5. A geodetic surveying instrument, configured to move a measurement light beam into a desired measurement direction in space, the geodetic surveying instrument comprising:
at least one movement axis which is motorized for providing a positioning of the measurement direction of the geodetic surveying instrument;
an instrument-encoder at the movement axis configured for deriving the measurement direction as a measurement value of the geodetic surveying instrument; and
a transmission link of the movement axis of the geodetic surveying instrument to a motor axis of a stepper motor,
wherein the transmission link is configured with a gear reduction and a slipping clutch arrangement, and
wherein the stepper motor comprises a rotational motor-encoder on its motor-axis and is driven by a motor controller that provides a field oriented control of phase currents of the stepper motor, which field orientation is derived based on the rotational motor-encoder,
wherein the stepper motor is a bipolar two phase stepper motor and the field oriented control is provided as two phase field-oriented control (FOC) controller unit.

6. A geodetic surveying instrument, configured to move a measurement light beam into a desired measurement direction in space, the geodetic surveying instrument comprising:
at least one movement axis which is motorized for providing a positioning of the measurement direction of the geodetic surveying instrument;
an instrument-encoder at the movement axis configured for deriving the measurement direction as a measurement value of the geodetic surveying instrument; and
a transmission link of the movement axis of the geodetic surveying instrument to a motor axis of a stepper motor,
wherein the transmission link is configured with a gear reduction and a slipping clutch arrangement, and
wherein the stepper motor comprises a rotational motor-encoder on its motor-axis and is driven by a motor controller that provides a field oriented control of phase currents of the stepper motor, which field orientation is derived based on the rotational motor-encoder,
wherein the rotational motor-encoder is configured with a rotational resolution that is higher than a steps per revolution count of the stepper motor.

7. A geodetic surveying instrument, configured to move a measurement light beam into a desired measurement direction in space, the geodetic surveying instrument comprising:
at least one movement axis which is motorized for providing a positioning of the measurement direction of the geodetic surveying instrument;
an instrument-encoder at the movement axis configured for deriving the measurement direction as a measurement value of the geodetic surveying instrument; and
a transmission link of the movement axis of the geodetic surveying instrument to a motor axis of a stepper motor,
wherein the transmission link is configured with a gear reduction and a slipping clutch arrangement, and
wherein the stepper motor comprises a rotational motor-encoder on its motor-axis and is driven by a motor controller that provides a field oriented control of phase currents of the stepper motor, which field orientation is derived based on the rotational motor-encoder
wherein an electronics printed circuit board (PCB) is directly mechanically attached to an end face of the stepper motor, which electronics PCB comprises a motor driver power electronics and a motor controller unit comprising at least control loops for the field oriented control of the stepper motor.

8. The geodetic surveying instrument according to claim 7 , wherein the electronics PCB mechanically comprises at least a portion of the rotational motor-encoder.

9. A geodetic surveying instrument, configured to move a measurement light beam into a desired measurement direction in space, the geodetic surveying instrument comprising:
at least one movement axis which is motorized for providing a positioning of the measurement direction of the geodetic surveying instrument;
an instrument-encoder at the movement axis configured for deriving the measurement direction as a measurement value of the geodetic surveying instrument; and
a transmission link of the movement axis of the geodetic surveying instrument to a motor axis of a stepper motor,
wherein the transmission link is configured with a gear reduction and a slipping clutch arrangement, and
wherein the stepper motor comprises a rotational motor-encoder on its motor-axis and is driven by a motor controller that provides a field oriented control of phase currents of the stepper motor, which field orientation is derived based on the rotational motor-encoder
wherein the rotational motor-encoder is a magnetic angular encoder or an optical angular encoder or a capacitive angular encoder with a code-disk attached to the motor-axis.

10. A method for driving a movement axis of a geodetic surveying instrument, the method comprising:
deriving a motor axis orientation by a rotational motor axis encoder on a motor axis of a stepper motor;
controlling phase currents of the stepper motor according to a field oriented control according to the axis encoder by a FOC driver;
transmitting a movement of the motor axis to an instrument axis by a gear reduction and a slipping clutch;
deriving a measurement direction of the instrument by an instrument axis encoder on the instrument axis; and
controlling the FOC driver according to the instrument axis encoder for a positioning of the measurement direction.

11. The method according to

Assignees

• Leica Geosystems Ag

Inventors

• Müller Benjamin
• Schmitt Thomas Lienhard
• Herbst Christoph
• Wachter Hannes Martin

Classifications

• G01C1/02

  Theodolites · CPC title

• B25F5/001

  Gearings, speed selectors, clutches or the like specially adapted for rotary tools · CPC title

• B25B21/00

  Portable power-driven screw or nut setting or loosening tools; (details or components, e.g. casings, bodies, of portable power-driven tools not particularly related to the operation performed B25F5/00; {for mounting or dismounting wheels B60B29/006}); Attachments for drilling apparatus serving the same purpose (machines B23P19/06) · CPC title

• G01C15/002 Primary

  Active optical surveying means (optical plumbing G01C15/105) · CPC title