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Intelligent Hybrid Sensor Utilizing 3D Laser Vision Provides Unique Solutions for the Material Handling and Product Measurement Market

by Michel Seers / Jeffrey Noruk / Mr. Shin , Advanced Robot Application Manager, Servo-Robot Inc., Quebec, Canada / President, Servo-Robot Corp., USA / CEO & President, SRK Corporation, Korea
Servo-Robot Inc.

Abstract/Introduction

Material handling is traditionally done utilizing a robot integrated to a 2D vision system with the camera(s) either mounted to the robot or fixed in place. While there have been many successes over the years with this approach, there are some limitations with 2D vision which can prevent total success from occurring. A hybrid sensor utilizing ultrasonic range finding, 3D laser scanning and 2D web viewing can provide a superior solution. Two successful projects utilizing this approach are presented below.

Project 1 - Robotic Automotive Body Panel Auto Racking and Feature Verification 

The project involved robotically picking up painted door panels off a conveyor and placing them into a rack for delivery to the assembly line. The panels had holes pierced in areas where there were embossed raised areas. A comparison chart shown in Figure 1 was done by the integrator to help determine whether a traditional 2D camera approach or the hybrid 3D scanning technique would be more effective. Note that several tests were run with both systems to get the required data.

Figure 1 – 2D versus 3D Hybrid Sensor Comparison

To better understand the RoboPal sensor package, see Figures 2A, 2B and 3 below which provide the technical specifications and functional capabilities. 

 

Figure 2A – RoboPal Sensor With Field of View Dimensions

Figure 2B - Sensor Technical Specifications (mm)

Figure 3 – Robo-Pal Functions

For this project, the robotically mounted 3D hybrid sensor is used in the following manner.

Sequence

  1. Stack of panels are moved into the robot working envelope
  2. Robot utilizes the ultrasonic sensor to quickly find the top of the stack
  3. Robot moves to the first program point and searches for blank edge
  4. Robot moves to other programmed points and determines the offset location
  5. The robot original program is adjusted
  6. Robot picks up the panel and places into the rack
  7. Optional: Measure one critical hole for size and location.

Note: The measurement of the hole size and location was especially conducive for the 3D laser hybrid sensor because it could automatically handle the multiple surfaces associated with the embossment around the hole which was not easily done with 2D vision.

Summary of advantages and payback comparison

The advantages of the robotic 3D hybrid sensor were improved accuracy, increased robustness and less integration and startup time.

Project 2 – Robotic loading of a steel ingot into a furnace

The application involved picking ingots off a pallet brought in by a conveyor to a roughly located position.  See Figure 4 showing the robotic system. The pallet has many ingots on it with several layers present. The overall size of the pallet is 1m X 1m X 2m (high). The ingot location was variable due to: a) pallet location tolerance on the conveyor, b) the rough location of the ingots on the pallet and c) the inconsistent shape of the ingots themselves.   Both 2D and 3D sensing methods were considered, but a robotically mounted 3D camera approach was selected over a fixed camera(s) method.  Note that mounting a 2D camera to the robot in this case was not possible due to the hot environment that it would have been subjected to.  The reasons for this selection decision were:

  1. The cycle time allowed for the use of one camera mounted to a robot versus multiple fixed 2D cameras mounted above.
  2. Access to the area above the pallet was not extremely conducive to mounting the cameras.
  3. The hybrid sensors’ ultrasonic and 3D vision provided a unique solution as shown by the following description.
    1. Robot moves to start position prior to locating and measuring sequence.
    2. Robot moves full speed to locate the top of the ingot layer utilizing UT range finding.
    3. Once the top layer is found, the robot scans to locate the position of all ingots with a cycle time of 40 seconds.
    4. Robot then picks up the first ingot and loads it into the furnace.  Time to find, pickup and load the ingot is less than 5 seconds.  The actual locating is done with the precise 3D laser in less than 2 seconds.
    5. Robot proceeds to remove ingots from the pallet.  If for some reason an ingot is missing, the robot is automatically told to skip it.
  4. The hybrid sensor was capable of not only identifying that the right ingots are on the pallet but also that the ingot shape is correct. 

  1. While the web cam capability is also seen as an advantage, it is not used directly in the pick up operation. It is employed now only for general viewing to determine the overall status.

Figure 4 – Robo-Pal used for Magnesium Ingot handling system

Figure 4 – Robo-Pal used for Magnesium Ingot handling system

 

 

 

The robotic hybrid sensor solution has been quite successful with respect to cycle time and reliability. The programming is straight forward and quick to modify for different ingot shapes. Remote diagnostic monitoring is utilized by the integrator to verify the operation is working properly and to troubleshoot 24/7.

 

Conclusions

  1. A robotic 3D hybrid sensor is a superior solution to a traditional fixed 2D camera approach for many applications including the two described in this article.
  2. Advantages include insensitivity to changing lighting, no problems with material color variations, better measurement accuracy and quicker startup due to reduced integration time.
  3. Although the initial capital equipment investment is sometimes higher with robotic 3D laser sensors versus 2D fixed cameras, the payback is generally in the range of 3-6 months because of reduced integration costs (less tests and verification required) and a reduced life cycle cost due to higher system reliability. In fact, sometimes the payback is realized before the system is even put into production.

Credits & Contact:
Michel Seers, Advanced Robot Application Manager, Servo-Robot Inc., Quebec, Canada
Jeffrey Noruk, President, Servo-Robot Corp., USA
Mr. Shin, CEO & President, SRK Corporation, Korea

Contact:
Servo-Robot Inc. +1 (450) 653-7868
Website: www.servorobot.com

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