Method of operating a stepper motor in a dental tool machine

Patent metadata

Field	Value
Publication number	US-12028012-B2
Application number	US-202017626252-A
Country	US
Kind code	B2
Filing date	Jul 8, 2020
Priority date	Jul 11, 2019
Publication date	Jul 2, 2024
Grant date	Jul 2, 2024

Abstract

A method of operating a stepper motor for use in a dental tool machine for removing material from a dental blank, the method including: a step of adapting torque reserves of the stepper motor at operating points to net load moments respectively. The method includes a first step of predicting, through simulation, the net load moments beforehand; a second step of predicting, through simulation, the supply current to be supplied to the stepper motor for setting up the torque reserves that correspond to the predicted net load moments respectively; and a step of driving the stepper motor based on the predicted supply current.

First claim

The invention claimed is:

1. A method of operating a stepper motor for use in a dental tool machine for removing material from a dental blank, the method comprising: a step of adapting without use of any rotary encoder-based regulation torque reserves of the stepper motor at operating points to net load moments (M_net) about the rotational axis of the stepper motor respectively, wherein the adapting step comprises: a first step (S1) of predicting, through simulation, the net load moments (M_net) beforehand; a second step (S2) of predicting, through simulation, the supply current (I_tr) to be supplied to the stepper motor for setting up the torque reserves that correspond to the predicted net load moments (M_net) respectively; and further comprising: a step (S3) of operating the stepper motor based on the predicted supply current (I_tr), wherein the net load moments (M_net) corresponds to a superposition of the load moments (M_df, M_mf) respectively due to drive forces arising through a drive train of the stepper motor and the machining forces arising through the material removal from the dental blank which are respectively predicted in the first predicting step based on a drive train simulation (S_dt) and a material removal simulation (S_mr) of the dynamic acceleration/deceleration along a drive train trajectory corresponding to the movement of the dental tool, and the dental tool trajectory.

2. The method according to claim 1 wherein the supply current (I_tr) is predicted in the second predicting step (S2) based on a torque reserve simulation (S_tr) of a dynamic current supply.

3. The method according to claim 1 , wherein the first and second predicting steps (S1,S2) are performed in advance of the driving step (S3).

4. The method according to claim 1 , further comprising: a step of generating an enhanced supply current (I_tr′) by adding to the predicted supply current (I_tr) a constant amount and/or by multiplying the predicted supply current (I_tr) through a constant factor greater than one, wherein the stepper motor is driven based on the enhanced supply current (I_tr′).

5. The method according claim 1 , further comprising: a step of generating a step shaped supply current (I_tr″) having two or more levels based on the predicted supply current (I_tr), wherein the stepper motor is driven based on the step shaped supply current (I_tr″).

6. The method according to claim 5 , wherein the stepper motor is driven based on a smoothed step shaped supply current (I_tr″) which is obtained by at least one of interpolation, morphing and filtering thereof.

7. The method according to claim 5 , wherein the step shaped supply current (I_tr″) has at least two levels, wherein a relatively lower level is used for finishing the dental blank and a relatively higher level is used for roughing the dental blank.

8. The method according to claim 5 , wherein the step shaped supply current (I_tr″) has at least two levels, wherein a relatively lower level is used for making partial cut paths in the dental blank and a relatively higher level is used for making full cut paths in the dental blank.

9. The method according to claim 5 , wherein the step shaped supply current (I_tr″) has at least two levels, wherein a relatively lower level is used for machining with a first type of dental tool and a relatively higher level is used for machining with a second type of dental tool different than the first type of dental tool.

10. The method according to claim 5 , wherein the step shaped supply current (I_tr″) has at least two levels, wherein a relatively lower level is used for lubricated machining of the dental blank and a relatively higher level is used for dry machining of the dental blank.

11. The method according to claim 5 , wherein the step shaped supply current (I_tr″) has at least two levels, wherein a relatively lower level is used for a first revolution speed of the dental tool and a relatively higher level is used for a second revolution speed of the dental tool different than the first revolution speed.

12. The method according to claim 5 , wherein the step shaped supply current (I_tr″) has at least two levels, wherein a relatively lower level is used for a first type of material of the dental blank and a relatively higher level is used for a second type of material of the dental blank different than the first type of material.

13. The method according to claim 5 , wherein the step shaped supply current (I_tr″) has at least two levels, wherein a relatively lower level is used for a relatively low acceleration of a carriage of the dental tool and a relatively higher level is used for a relatively high acceleration of the carriage of the dental tool.

14. The method according to claim 5 , wherein the step shaped supply current (I_tr″) has at least two levels, wherein a relatively lower level is used for a first velocity of a carriage of the dental tool and a relatively higher level is used for a second velocity of the carriage of the dental tool different than the first velocity.

15. The method according to claim 5 , wherein the step shaped supply current (I_tr″) has at least two levels, wherein a relatively lower level is used for a low jerk in the trajectory of a carriage of the dental tool and a relatively higher level is used for a high jerk in the trajectory of the carriage of the dental tool.

16. A dental tool machining system comprising: a dental tool machine for removing material from at least one dental blank, wherein the dental tool machine has one or more stepper motors for driving a carriage that movably holds one or more dental tools and one or more stepper motors for driving a retainer which movably holds the dental blanks; a control means for operating the stepper motors; wherein the control means is further adapted to operate the stepper motors in accordance with claim 1 .

17. A program comprising computer readable codes for causing a computer-based dental tool machine to carry out the method steps according to claim 1 .

18. A non-transitory computer readable storage medium which stores the program according to claim 17 .

Assignees

• Dentsply Sirona Inc

Inventors

• Schneider Hans-Christian
• Trautmann Daniel

Classifications

• A61C13/0004

  Computer-assisted sizing or machining of dental prostheses · CPC title

• A61C13/0006

  Production methods · CPC title

• H02P8/32

  Reducing overshoot or oscillation, e.g. damping · CPC title

• H02P8/18 Primary

  Shaping of pulses, e.g. to reduce torque ripple {(Reducing overshoot H02P8/32 takes precedence)} · CPC title