US 11,192,243 B2Granted

Method, constraining device and system for determining geometric properties of a manipulator

AssigneeCognibotics AB

InventorsKlas Nilsson, Adam Nilsson, Andreas Stolt, Olof Sornmo, Martin Holmstrand, Niklas Nilsson

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Abstract

A method and system for determining geometric properties of a manipulator (2). The manipulator (2) is controlled to perform constrained motions exhibiting force interaction with the environment, or between different links of the manipulator (2), such that a kinematic chain is formed mechanically. The chain may include peripherals and external axes of motion. A constraining device, enables motions that facilitate the determination of geometric properties. A unified model of joint and link compliances facilitates determination of stiffness parameters. The force interaction is controlled with awareness of friction such that non-geometric properties are possible to identify, thereby enabling separation of non-geometric effects from the geometric ones, which improves accuracy.

Claims35

Dependent claims

Method for determining at least one geometric property of a manipulator that influences end-effector motions of the manipulator, wherein the manipulator is arranged to be controlled by a control system for moving an end-effector of the manipulator to target poses, and wherein the manipulator comprises at least two axes, of which at least one axis comprises at least one elasticity and is affected by friction effects, the method comprising:

constraining motion of the manipulator, such that the motion of the manipulator is physically constrained in at least one degree of freedom, thereby enabling a constrained manipulator motion and correspondingly a constrained motor motion for the at least one axis;
commanding the manipulator to approach a set of target poses, where, for each target pose, a physical pose is reached in which the constrained manipulator motion can be performed, which includes a non-zero constrained motor motion;
performing friction-aware control of the constrained manipulator motion for a period of time, to accomplish well-defined friction forces/torques that can be separated from the friction effects, while monitoring quantities related to motor torque and to motor angle of the at least one axis;
performing an identification of a set of kinematic parameters for an elasto-kinematic model that includes at least one known quantity representing the at least one elasticity, the identification being based on the monitored quantities and on elastic properties of the manipulator, where the friction effects are excluded from the identification;
and
obtaining the at least one geometric property of the manipulator based on the identified set of kinematic parameters.

3 more elements

A system for determining at least one geometric property of a manipulator that influences motions of the manipulator, the system comprising a control system, wherein the manipulator is arranged to be controlled by the control system for moving an end-effector of the manipulator to target poses, and wherein the manipulator comprises at least two axes, of which at least one axis comprises at least one elasticity and is affected by friction effects, characterized in that the manipulator is constrained by a constraining device such that the motion of the manipulator is physically constrained in at least one degree of freedom, thereby to enable a constrained manipulator motion and correspondingly a constrained motor motion for the at least one axis, wherein the control system is operable to:

command the manipulator to approach a set of target poses, where, for each target pose, a physical pose is reached in which the constrained manipulator motion can be performed, which includes a non-zero constrained motor motion;
perform friction-aware control of the constrained manipulator motion for a period of time, to accomplish well-defined friction forces/torques that can be separated from the friction effects, while monitoring quantities related to motor torque and to motor angle of the at least one axis;
perform an identification of a set of kinematic parameters for an elasto-kinematic model that includes at least one known quantity representing the at least one elasticity, the identification being based on the monitored quantities and on elastic properties of the manipulator, where the friction effects are excluded from the identification;
and
obtain the at least one geometric property of the manipulator based on the identified set of kinematic parameters.

2 more elements

Dependencies are inferred from the claim text.

Facts

Application: 16/089,282Filed 27 Mar 2017
Priority: EP 1616269529 Mar 2016
Published: US 2020/0298403 A124 Sep 2020
Granted: 7 Dec 2021
Term ends: Not estimatedThe source records don’t support an estimate.

Classification16 codes

B25J 9/1633
Characterised by the control loop: compliant, force, torque control, e.g. combined with position control
G05B 19/401
Numerical control [NC], i.e. automatically operating machines, in particular machine tools, e.g. in a manufacturing environment, so as to…
B23Q 3/15713
Of rotary tools: a transfer device taking a single tool from a storage device and inserting it in a spindle
B25J 9/1653
Characterised by the control loop: parameters identification, estimation, stiffness, accuracy, error analysis