Method for controlling an electric cylinder and a control system for the electric cylinder

• US 8,749,180 B2
• Filed: 04/07/2011
• Issued: 06/10/2014
• Est. Priority Date: 06/25/2010
• Status: Active Grant

• Current Assignee: Sintokogio Limited
• Original Assignee: Sintokogio Limited
• Inventors: Nagasaka, Masahiko, Shirai, Yoichiro
• Primary Examiner(s): Ip, Paul
• Application Number:
  US13/575,450
• Publication Number:
  US 20130088182A1
• Time in Patent Office: 1,160 Days
• Field of Search: 318/566, 318/135, 318/468, 318/490, 318/625, 318/400.08, 100/35, 100/45
• US Class Current: 318/135
• CPC Class Codes: B30B 15/0094 Press load monitoring means B30B15/281 takes precedence
• CPC Class Codes: B30B 15/166 Electrical control arrangements
• CPC Class Codes: B30B 15/281 overload limiting devices in general F16H35/10
• CPC Class Codes: B30B 15/284 releasing fluid from a fluid chamber subjected to overload pressure
• CPC Class Codes: G05B 11/36 with provision for obtaining particular characteristics, e.g. proportional, integral, differential
• CPC Class Codes: G05B 19/406 characterised by monitoring or safety G05B19/19 takes precedence

Abstract

The present invention is aimed to realize a method and a system for controlling an electric cylinder by which the load detector that is attached to an electric cylinder and the rod of the cylinder can avoid being overloaded. An unexpected bump between the rod of the cylinder and the material to be pressed can cause that overload.

A servo controller 17 determines whether the load for pressurizing Pm detected by the load detector 13 is larger than or equal to the load for detecting a bump Pc. If it is determined that the load for pressurizing Pm is larger than or equal to the load for detecting a bump Pc, the servo controller 17 determines whether the flag for stopping is ON. Also, the controller 17 determines whether the speed Sm of the rod 11 is greater than or equal to an allowable speed to bump Sc. If it is determined that the flag for stopping is ON or if it is determined that the speed Sm of the rod 11 is greater than or equal to an allowable speed to bump Sc, then the rod 11 is crash stopped by providing to a servo amplifier 16 a command pulse signal for positioning in the reverse direction and by decreasing the number of stored pulses in the amplifier 16.

Claims

1. A method for controlling an electric cylinder in a device, wherein

the device comprises

an electric cylinder that moves a rod,

a load detector attached to the rod that detects the load for pressurizing applied to a material to be pressed,

a servomotor that drives the electric cylinder, and

a position detector attached to the servomotor that is electrically connected to a servo amplifier, wherein

the servo amplifier is electrically connected to the servomotor and to a servo controller and controls the movement of the servomotor, and wherein

the servo controller is electrically connected to the load detector and the servo amplifier and outputs a control command to the servo amplifier so as to control the servomotor, wherein

the method comprises:

a step for controlling the movement of the rod, wherein in the servo controller a speed of the rod, a load for detecting a bump between the rod and the material to be pressed, a flag for stopping determining whether the driving of the rod should be allowed if the bump between the rod and the material is detected, and an allowable speed to bump for determining whether the speed of the rod is the value at which the rod should be crash stopped, are set, and wherein

the servo controller drives the rod based on the speed of driving that has been input into the controller, and causes the load detector to provide to the servo controller a signal for the load for pressurizing corresponding to the load for pressurizing detected by the load detector, and wherein the following steps take place;

a step for detecting a bump, wherein the servo controller determines whether the load for pressurizing is larger than or equal to the load for detecting a bump between the rod and the material, based on the signal for the load for pressurizing,

a step for detecting a flag for stopping when a bump occurs, wherein the servo controller determines whether the flag is ON,

a step for detecting an allowable speed to bump, wherein if the flag is OFF at the step for detecting the flag the servo controller determines whether the speed of the rod is greater than or equal to an allowable speed to bump, and

a step for crash stopping, wherein if it is determined that the load for pressurizing is larger than or equal to the load for detecting the bump at the step for detecting a bump and it is determined that the flag is ON at the step for detecting a flag for stopping, or if it is determined that the speed of the rod is greater than or equal to the allowable speed to bump at the step for detecting an allowable speed to bump, then the rod is crash stopped by braking the rod or driving the rod in the reverse direction.

2. The method for controlling the electric cylinder of claim 1, wherein when the movement of the servomotor is controlled in a position-control mode the step for crash stopping comprises the following:

a step for computing the number of stored pulses, wherein the servo controller computes the number of stored pulses by subtracting the number of pulses from a feedback pulse signal from the number of pulses of the command pulse signal for positioning, wherein the command pulse signal for positioning is the signal when the determination is done at the step for detecting a flag for stopping or at the step for detecting an allowable speed to bump, and wherein the feedback pulse signal is provided by the servo amplifier to the servo controller based on the signal denoting the absolute position that is provided by the position detector to the servo amplifier and that corresponds to the number of rotations of the servomotor, and

a step for outputting a command pulse signal for positioning in the reverse direction, wherein the servo controller provides to the servo amplifier the command pulse signal that is a position control pulse signal that decreases the number of stored pulses based on the number computed at the step for computing them.

3. The method for controlling the electric cylinder of claim 2, wherein the number of pulses of the command pulse signal for positioning in the reverse direction is greater than or equal to the number of the stored pulses.

4. The method for controlling the electric cylinder of claim 2, wherein the frequency of the command pulse signals for positioning in the reverse direction is greater than or equal to the frequency of the pulses of the command for positioning.

5. The method for controlling the electric cylinder of claim 1, wherein when the movement of the servomotor is controlled in a position-control mode the step for crash stopping comprises a step for stopping providing the command pulse signal for positioning by which the servo controller stops providing the command pulse signal for positioning to the servo amplifier, to thereby stop the rod.

6. The method for controlling the electric cylinder of claim 1, wherein when the movement of the servomotor is controlled in a speed-control mode the step for crash stopping comprises a step for stopping providing the speed command signal by which the servo controller stops providing the speed command signal to the servo amplifier.

7. The method for controlling the electric cylinder of claim 1, wherein when the movement of the servomotor is controlled in a speed-control mode the step for crash stopping comprises a step for providing from the servo controller to the servo amplifier a reverse signal that reverses the speed command signal and drives the rod in the reverse direction to that for pressurizing.

8. The method for controlling the electric cylinder of claim 1, wherein when the movement of the servomotor is controlled in a torque-control mode the step for crash stopping comprises a step for stopping providing the torque command signal by which the servo controller stops providing the torque command signal to the servo amplifier.

9. The method for controlling the electric cylinder of claim 1, wherein when the movement of the servomotor is controlled in a torque-control mode the step for crash stopping comprises a step for providing from the servo controller to the servo amplifier a reverse signal that reverses the torque command signal and drives the rod in the reverse direction to that for pressurizing.

10. A system for controlling an electric cylinder in a device, wherein

the device comprises the following:

an electric cylinder that moves a rod,

a load detector attached to the rod that detects the load for pressurizing applied to a material to be pressed,

a servomotor that drives the electric cylinder, and

a position detector attached to the servomotor that is electrically connected to a servo amplifier, wherein

the servo amplifier is electrically connected to the servomotor and to a servo controller and controls the movement of the servomotor, and wherein

the servo controller is electrically connected to the load detector and the servo amplifier and outputs a control command to the servo amplifier so as to control the servomotor, wherein

the servo controller is configured to be able to set a speed of the rod, a load for detecting a bump between the rod and the material to be pressed, a flag for stopping determining whether the driving of the rod should be allowed if the bump between the rod and the material is detected, and an allowable speed to bump for determining whether the speed of the rod is the value at which the rod should be crash stopped, and wherein

the servo controller drives the rod based on the speed of driving, determines whether the load for pressurizing detected by the load detector is larger than or equal to the load for detecting a bump, and if it is determined that the load for pressurizing is larger than or equal to the load for detecting a bump then the servo controller determines whether the flag for stopping is ON and the servo controller also determines whether the speed of the rod is greater than or equal to an allowable speed to bump, and if it is determined that the flag for stopping is ON or if it is determined that the speed of the rod is greater than or equal to an allowable speed to bump, then the rod is crash stopped by braking the rod or driving the rod in the reverse direction.

11. The system for controlling the electric cylinder of claim 10, wherein when the movement of the servomotor is controlled in a position-control mode the crash stop is carried out by

computing the number of stored pulses, wherein the servo controller computes the number of stored pulses by subtracting the number of pulses of a feedback pulse signal from the number of pulses of the command pulse signal for positioning, wherein the command pulse signal for positioning is the signal denoting when the servo controller detects a flag for stopping or detects an allowable speed to bump, and the feedback pulse signal is provided by the servo amplifier to the servo controller based on the signal denoting the absolute position that is provided by the position detector to the servo amplifier and that corresponds to the number of rotations of the servomotor,

outputting a command pulse signal for positioning in the reverse direction, wherein the servo controller provides to the servo amplifier the command pulse signal that is a position control pulse signal that decreases the number of stored pulses based on the number of stored pulses, and

causing the number of stored pulses in the servo amplifier to decrease, to thereby immediately stop the rod.

12. The system for controlling the electric cylinder of claim 11, wherein the number of pulses of the command pulse signal for positioning in the reverse direction is greater than or equal to the number of stored pulses.

13. The system for controlling the electric cylinder of claim 11 or 12, wherein the frequency of the command pulse signals for positioning in the reverse direction is more than or equal to the frequency of the pulses of the command for positioning.

14. The system for controlling the electric cylinder of claim 10, wherein when the movement of the servomotor is controlled in a position-control mode the crash stop is carried out by the servo controller by stopping providing the command pulse signal for positioning to the servo amplifier, to thereby stop the rod.

15. The system for controlling the electric cylinder of claim 10, wherein when the movement of the servomotor is controlled in a speed-control mode the crash stop is carried out by the servo controller by stopping providing the speed command signal to the servo amplifier, to thereby stop the rod.

16. The system for controlling the electric cylinder of claim 10, wherein when the movement of the servomotor is controlled in a speed-control mode, the crash stop is carried out by the servo controller by providing to the servo amplifier a reverse signal that reverses the speed command signal and drives the rod in the reverse direction to that for pressurizing.

17. The system for controlling the electric cylinder of claim 10, wherein when the movement of the servomotor is controlled in a torque-control mode, the crash stop is carried out by the servo controller by stopping providing the torque command signal to the servo amplifier, to thereby stop the rod.

18. The system for controlling the electric cylinder of claim 10, wherein when the movement of the servomotor is controlled in a torque-control mode the crash stop is carried out by the servo controller by providing to the servo amplifier a reverse signal that reverses the torque command signal and drives the rod in the reverse direction to that for pressurizing.