US 10,851,810 B2Granted

Actuator limit controller

AssigneeBoston Dynamics, Inc.

InventorsAlex Perkins, Kevin Blankespoor, Alfred Rizzi

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Abstract

In some applications, a piston of a hydraulic actuator may move at high speeds, and large undesired forces may be generated if the piston reaches an end-stop of the hydraulic actuator at a high speed. The undesired forces may, for example, cause mechanical damage in the hydraulic actuator. A controller may receive information indicative of the piston reaching a first position at a first threshold distance from the end-stop, and, in response, may modify a signal to a valve assembly controlling flow of hydraulic fluid to and from the hydraulic actuator. Further, the controller may receive information indicative of the piston reaching a second position at a second threshold distance closer to the end-stop of the hydraulic actuator, and, in response, the controller may further modify the signal to the valve assembly so as to apply a force on the piston in a away from the end-stop.

Claims20

Dependent claims

A method for controlling speed of a piston slidably disposed in a cylinder cavity of a hydraulic actuator, the method comprising:

receiving, at a controller, a velocity command for moving the piston within the cylinder cavity of the hydraulic actuator at a desired velocity in a first linear direction toward an end-stop of the hydraulic actuator, the piston comprising a piston head dividing the cylinder cavity into a first chamber and a second chamber, the first chamber disposed between the piston head and the end-stop;
and
as the piston moves in the first linear direction toward the end-stop based on the velocity command:
receiving, at the controller, a velocity feedback signal indicating an instantaneous velocity of the piston;
determining, by the controller, a velocity error signal indicating a velocity difference between the desired velocity of the piston and the instantaneous velocity of the piston indicated by the velocity feedback signal;
receiving, by the controller, position information indicating a position of the piston relative to the end-stop;
when the position of the piston relative to the end-stop is greater than a first threshold distance, multiplying, by the controller, the velocity error signal by a proportional gain value to cause the instantaneous velocity of the piston to maintain the desired velocity;
and
when the position of the piston relative to the end-stop is equal to or less than the first threshold distance:
decreasing a magnitude of the proportional gain value;
and
multiplying, by the controller, the velocity error signal by the decreased magnitude of the proportional gain value to cause the instantaneous velocity of the piston to decrease from the desired velocity.

9 more elements

A system comprising:

a source of pressurized hydraulic fluid;
a return line;
a hydraulic actuator comprising:
a cylinder defining a cylinder cavity and having an end-stop;
and
a piston slidably disposed in the cylinder cavity of the cylinder and comprising a piston head, the piston head dividing the cylinder cavity into a first chamber and a second chamber, the first chamber disposed between the piston head and the end-stop;
a valve assembly configured to selectively couple or decouple the source of pressurized hydraulic fluid to the second chamber and selectively couple or decouple the first chamber to the return line;
and
a controller in communication with the valve assembly, the controller configured to perform operations comprising:
receiving a velocity command for moving the piston within the cylinder cavity at a desired velocity in a first linear direction toward the end-stop;
and
as the piston moves in the first linear direction toward the end-stop based on the velocity command:
receiving a velocity feedback signal indicating an instantaneous velocity of the piston;
determining a velocity error signal indicating a velocity difference between the desired velocity of the piston and the instantaneous velocity of the piston indicated by the velocity feedback signal;
receiving position information indicating a position of the piston relative to the end-stop;
when the position of the piston relative to the end-stop is greater than a first threshold distance, multiplying the velocity error signal by a proportional gain value to cause the instantaneous velocity of the piston to maintain the desired velocity;
and
when the position of the piston relative to the end-stop is equal to or less than the first threshold distance:
decreasing a magnitude of the proportional gain value;
and
multiplying the velocity error signal by the decreased magnitude of the proportional gain value to cause the instantaneous velocity of the piston to decrease from the desired velocity.

18 more elements

Dependencies are inferred from the claim text.

Facts

Application: 16/550,903Filed 26 Aug 2019 · continuation
Priority: 24 Jul 2014
Published: US 2019/0376533 A112 Dec 2019
Granted: 1 Dec 2020
Term ends: Not estimatedThe source records don’t support an estimate.

Classification20 codes

F15B 11/048
Depending on the position of the working member: with deceleration control
F15B 9/09
Controlled by valves affecting the fluid feed or the fluid outlet of the servomotor: with electrical control means
F15B 15/22
Other details , e.g. assembly with regulating devices: for accelerating or decelerating the stroke
F15B 15/28
Other details , e.g. assembly with regulating devices: means for indicating the position, e.g. end of stroke

Family

Application62/028,546Us provisional application · filed 24 Jul 2014
Application14/489,778Parent of this continuation · filed 18 Sep 2014
Application15/373,626Parent of this continuation · filed 9 Dec 2016
US 9,546,672 B2Parent of this continuation · filed 17 Jan 2017
US 2019/0376533 A1Pre-grant publication · published 12 Dec 2019
US 10,550,860 B2Parent of this continuation
US 2016/0025114 A1Published application
US 2017/0089365 A1Published application
US 10,851,810 B2This patent

From the US filing history. Foreign family members aren’t listed.