CN-121989293-A - Method and system for setting payload weight value of industrial robot

CN121989293ACN 121989293 ACN121989293 ACN 121989293ACN-121989293-A

Abstract

A method, system for setting a payload weight value for an industrial robot, wherein one or more objects are picked up by a robot gripper, the weight of the objects is automatically determined by a force sensor and the weight is used for the payload, and the payload value is automatically adjusted when any object is discharged. When all objects are known to be of the same weight, only one weight measurement is required, and objects of different weights can be processed by weight measurements made for each object. The system automatically handles payload adjustments without requiring manual adjustments or custom programming. The robot uses the payload weight value upon detecting any externally applied force indicative of contact with an operator or other object, and also serves to ensure that the payload acceleration does not exceed the gripping force capability or robot joint load limit.

Inventors

YU HAOCHEN
Jack Weinmann
Garnesh Kalbavi

Assignees

发纳科美国公司

Dates

Publication Date: 20260508
Application Date: 20251031
Priority Date: 20251016

Claims (20)

1. A method for setting a payload weight value of an industrial robot, the method comprising: Providing a plurality of objects which can be grasped; gripping a number of said objects by means of grippers provided to the robot; Measuring the total weight of the number of the objects using a load sensor provided to the robot or the gripper; Setting the payload weight value using the total weight of the number of the objects and including a known empty gripper weight value; When the gripped objects all have the same weight, determining the weight of each object as the total weight divided by the number, moving the gripper to a destination location, discharging a subset of the number of the objects, and reducing the payload weight value by an amount equal to the number of the discharged objects multiplied by the weight of each object, and When the gripped objects do not all have the same weight, moving the gripper to a destination position, discharging a subset of the number of objects, measuring a new weight of the reduced number of objects using the load sensor, and setting the payload weight value using the new weight.
2. The method of claim 1, further comprising discharging a next subset of the number of the objects and resetting the payload weight value until the gripper is empty, at which time the payload weight value is set to the empty gripper weight value.
3. The method of claim 1, wherein when the number of the objects is one and all the objects available for gripping have the same weight, gripping the one object, measuring only a weight of a first one of the objects, using the weight of the first one of the objects and including the known empty gripper weight value to set the payload weight value, discharging the one object, and repeatedly gripping and discharging additional ones of the objects without measuring a weight of each of the additional objects.
4. The method of claim 1, wherein when the number of the objects is one object and all the objects available for gripping do not have the same weight, gripping the one object, measuring the weight of the one object, using the weight of the one object and including the known empty gripper weight value to set the payload weight value, discharging the one object, and repeatedly gripping and discharging additional ones of the objects and including measuring the weight of each of the additional objects.
5. The method of claim 1, wherein the payload weight value is used to calculate a trajectory of the object moved by the robot, wherein the trajectory includes a spatial path of the gripper and a velocity and acceleration profile along the spatial path.
6. The method of claim 5, wherein calculating a trajectory comprises calculating a robot joint load and a gripper-object force based on the trajectory and the payload weight value, and when the robot joint load or the gripper-object force exceeds a corresponding predefined limit, recalculating the trajectory until the robot joint load and the gripper-object force do not exceed the limit.
7. The method of claim 5, wherein the robot is a collaborative robot configured for operation with a human operator proximate the robot, and wherein the payload weight value is further used to establish a threshold for an external force on the robot that triggers a stop of robot motion.
8. A method according to claim 1, wherein the robot performs a palletising or destacking operation by gripping and moving the objects.
9. The method of claim 1, wherein the gripper is a vacuum gripper comprising a plurality of individually and selectively activatable suction elements, wherein each of the objects is grasped by activating one or more of the suction elements and released by deactivating the one or more of the suction elements.
10. The method of claim 1, wherein a configuration parameter indicating whether the objects available for gripping all have the same weight is defined prior to gripping the number of the objects.
11. A method for setting a payload weight value of an industrial robot, the method comprising: providing a plurality of objects capable of being grasped, wherein configuration parameters are defined, and the configuration parameters indicate whether the objects capable of being grasped all have the same weight; Gripping a number of said objects by means of grippers provided to a robot, wherein said grippers are vacuum grippers comprising a plurality of individually and selectively activatable suction elements, wherein each of said objects is gripped by activating one or more of said suction elements; Measuring the total weight of the number of the objects using a load sensor provided to the robot or the gripper; Setting the payload weight value using the total weight of the number of the objects and including a known empty gripper weight value; Determining the weight of each object as the total weight divided by the number, moving the gripper to a destination location, discharging a subset of the number of the objects, and reducing the payload weight value by an amount equal to the number of the discharged objects multiplied by the weight of each object when the gripped objects all have the same weight; Moving the gripper to a destination position, discharging a subset of the number of the objects, measuring a new weight of the reduced number of objects using the load sensor, and setting the payload weight value using the new weight when the gripped objects do not all have the same weight, and Discharging a next subset of the number of the objects and resetting the payload weight value until the gripper is empty, at which time the payload weight value is set to the empty gripper weight value, Wherein the payload weight value is used to calculate a trajectory for moving the gripper to the destination position, wherein the trajectory comprises a spatial path of the gripper and a velocity and acceleration profile along the spatial path.
12. The method of claim 11, wherein when the number of the objects is one object, grabbing the one object, measuring the weight of the one object, using the weight of the one object and including the known empty holder weight value to set the payload weight value, dumping the one object, and repeatedly grabbing and dumping additional ones of the objects, the weight of each of the additional ones of the objects being measured only if the objects available for grabbing are not all of the same weight.
13. The method of claim 11, wherein calculating a trajectory comprises calculating a robot joint load and a gripper-object force based on the trajectory and the payload weight value, and when the robot joint load or the gripper-object force exceeds a corresponding predefined limit, recalculating the trajectory until the robot joint load and the gripper-object force do not exceed the limit.
14. The method of claim 13, wherein the robot is a collaborative robot configured for operation with a human operator proximate the robot, and wherein the payload weight value is further used to establish a threshold for an external force on the robot that triggers a stop of robot motion.
15. A system of robotic pick and place with automatic payload compensation, the system comprising: industrial robot, equipped with a gripper and a load sensor coupled to the robot and/or to the gripper, and A robot controller in communication with the robot, the gripper, and the load sensor, the controller configured to perform steps comprising: Gripping a certain number of objects from a plurality of objects which can be gripped by the gripper; Measuring a total weight of the number of the objects using the load sensor; Setting the payload weight value using the total weight of the number of the objects and including a known empty gripper weight value; Determining the weight of each object as the total weight divided by the number, moving the gripper to a destination location, discharging a subset of the number of the objects, and reducing the payload weight value by an amount equal to the number of the discharged objects multiplied by the weight of each object when the gripped objects all have the same weight, and When the gripped objects do not all have the same weight, moving the gripper to a destination position, discharging a subset of the number of objects, measuring a new weight of the reduced number of objects using the load sensor, and setting the payload weight value using the new weight.
16. The system of claim 15, wherein the controller is further configured to discharge a next subset of the number of the objects and reset the payload weight value until the gripper is empty, at which time the payload weight value is set to the empty gripper weight value.
17. The system of claim 15, wherein the controller is further configured to, when the number of the objects is one object and all the objects available for gripping have the same weight, grip the one object, measure only a weight of a first one of the objects, use the weight of the first one of the objects and include the known empty gripper weight value to set the payload weight value, discharge the one object, and repeatedly grip and discharge additional ones of the objects without measuring a weight of each of the additional objects.
18. The system of claim 15, wherein the controller is further configured to grasp the one object, measure the weight of the one object, use the weight of the one object and include the known empty gripper weight value to set the payload weight value, discharge the one object, and repeatedly grasp and discharge additional ones of the objects and include measuring the weight of each of the additional objects when the number of the objects is one object and all the objects that are available for grasping do not have the same weight.
19. The system of claim 15, wherein the payload weight value is used by the controller to calculate a trajectory for moving the object by the robot, wherein the trajectory includes a spatial path of the gripper and a velocity and acceleration profile along the spatial path.
20. The system of claim 19, wherein calculating a trajectory includes calculating a robot joint load and a gripper-object force based on the trajectory and the payload weight value, and when the robot joint load or the gripper-object force exceeds a corresponding predefined limit, recalculating the trajectory until the robot joint load and the gripper-object force do not exceed the limit.

Description

Method and system for setting payload weight value of industrial robot Cross Reference to Related Applications The present application claims the benefit of the priority date of U.S. provisional patent application serial No. 63/715,043 entitled "automated method for setting payload of collaborative robot (AUTOMATED METHOD TO SET PAYLOAD OF COLLABORATIVE ROBOT)" filed on 1 month 11 of 2024. Technical Field The application relates to a method and a system for setting a payload weight value of an industrial robot. Background The present disclosure relates generally to the field of industrial robot control, and more particularly to a method for automatically setting a payload weight value of a collaborative robot, wherein one or more objects are picked up by a robot gripper, the weight of the objects is automatically determined by a force sensor and the weight is used for the payload, and the payload value is automatically adjusted when any of the objects is discharged. Discussion of the related Art Industrial robots are well known for performing a wide range of manufacturing, assembly and material movement operations. Many of these operations and tasks are performed by an articulated robot (such as a five-axis robot or a six-axis robot) having a servo motor at each rotary joint. Control of such robots is provided in real time, wherein the motion program is divided into small motion increments, and the robot controller performs real-time feedback control calculations to calculate joint motor input commands that move the robot arm end tool center point along a prescribed trajectory. One common type of robotic task is material movement, which involves moving a parcel or workpiece from a starting location to a destination location. A specific application of this type is that the robot is equipped with a vacuum gripper tool and the robot picks up packages (e.g. boxes) and moves them to a specified location. This type of robotic operation is typically used for destacking or palletizing (i.e., moving boxes from a tray to a conveyor, or vice versa). In the above type of operation, it is necessary to know the weight of the "payload", or the weight of the object being moved by the robotic arm. The payload is generally considered to include a gripper (typically a vacuum gripper of considerable weight) that carries one or more boxes at any given time. The payload weight values are used to calculate the robot arm end trajectory and corresponding speeds and accelerations that keep the robot joint load within prescribed limits and that also prevent the box from being detached from the vacuum gripper. Some applications require the use of collaborative robots, which are robots designed for use with human operators in a workspace. The collaborative robot includes control features for preventing strong contact between the robot or its payload and a human operator. In collaborative robotic applications, in addition to the trajectory calculation purposes described above, payload weight values are also used to establish control parameters that detect contact with any obstacle in the workspace. Various methods have been used to set payload weight values for robots. In the simplest case, the robot moves only one box at a time, each box having the same weight, and the weight is known. In this case, the payload weight value is simply the weight of the gripper (if the gripper is not carrying a box) or the weight of the gripper plus the known box weight (if the gripper is carrying a box). However, most practical applications are more complex, involving boxes of various sizes and weights on a single pallet, and require a robot to pick up multiple boxes simultaneously, discharge some of the boxes at one location and other boxes at another location, and so forth. In applications such as these, determining the payload weight value can be complex and time consuming. One known technique for establishing payload weight values is to simply measure the weight of all the carried cases after each gripping or releasing operation. Weight measurement may be performed by a force sensor mounted on the robotic arm near the vacuum gripper. The disadvantage of this technique is that the robot must stop after each gripping or releasing operation and that the weight measurement takes a certain time. These measurement delays severely reduce the productivity of the robot performing the parcel movement. Even if the weight of the boxes is known (all boxes have the same weight, or the boxes have various known weights), most palletizing/destacking operations still require flexibility to grasp and release different numbers and combinations of boxes depending on the composition of the particular pallet. For example, in one task, the robot may need to grasp three boxes of different weight and discharge them one by one at different locations, and in the next task, the robot may need to grasp four boxes of the same weight and discharge them in two, one, and one quantit