CN1611331A - Movable manipulator system - Google Patents

Abstract

A mobile manipulator system includes a 3-degree-of-freedom mobile platform, a 5-degree-of-freedom manipulator, a vision system and a computer control system. The camera is installed on the top of the linear guide rail (5) of the manipulator. The mobile platform can realize all-round movement in three degrees of freedom of front and back, left and right, and rotation on the plane. The 5-degree-of-freedom manipulator is composed of 1 moving joint and 4 rotating joints, with flexible operation. The mobile manipulator can realize a wide range of mobile operation functions, such as moving and transferring documents between various offices, operating the elevator button to make the robot move between various floors, etc. A camera with rotation and tilt functions is used and installed on the top of the linear guide rail. The observation of the surrounding scenery can be realized through the high-precision rotation of the camera when the mobile platform does not move. When the manipulator is in a low working position, the camera can be controlled to look down to ensure that the end of the manipulator is within the viewing angle of the camera.

Description

Mobile Manipulator System

technical field

The invention relates to a mobile manipulator system, in particular to a mobile manipulator system comprising a 3-degree-of-freedom omnidirectional mobile platform and a 5-degree-of-freedom manipulator for realizing large-scale mobile operations.

Background technique

The mobile manipulator system consists of a manipulator fixed on a mobile platform. The manipulator is used to realize some actions such as grasping, operation, etc. The working space of the manipulator is expanded through the movement of the platform, so that the manipulator can perform tasks in a more suitable posture. The mobile manipulator is very suitable for working instead of people in various dangerous situations, such as removing explosives, garbage disposal, field exploration and space operations, etc. It is suitable for dealing with various complex industrial problems such as the welding and manufacturing of mobile manipulators for large ship hulls, etc., suitable for It is used to expand the service range of interaction and cooperation with people, such as operating elevators, opening doors, and moving objects. In recent years, the Mars Pathfinder, the risk-removing manipulator, the mobile welding manipulator, the office letter delivery mobile robot, etc., which have been successfully developed in succession in recent years, are all typical mobile manipulator systems. With the increasing maturity of related robotics, automatic control, computer vision and other technologies, mobile manipulators will play an important role in a wider range of fields.

The mobile manipulator system generally includes: mobile platform, manipulator, sensor and control system, etc. Mobile platforms that work in flat road environments such as offices are mostly driven by wheels. If they can realize all three degrees of freedom (front and back, left and right, and rotation) on the plane, they are omnidirectional mobile platforms; otherwise, they are non-omnidirectional mobile platforms. . The structure of the manipulator can be very simple, and an articulated industrial manipulator with 6 degrees of freedom can also be used to achieve grasping and manipulation tasks in any posture. Sensors usually include ultrasonic, infrared, visual sensors, etc., which are used to perceive external environmental information to achieve positioning, obstacle avoidance and other functions. The control system is usually composed of a computer and a control card, etc., to realize the signal processing of the sensor, the coordinated control of the mobile platform and the manipulator.

In the construction of the mobile manipulator system, the mobile platform and the manipulator are generally combined simply, without considering the optimization of the overall system structure and performance. A simple mobile manipulator system consists of a mobile platform and a simple gripper, similar in basic structure and function to a forklift. For example, the system developed by V.Kumar et al. (T.G.Sugar, and V.Kumar, Control of cooperating mobile manipulators.IEEE Transactions on Robotics and Automation, 2002, 18(1): 94-103) includes an omnidirectional mobile platform and a clip, And a 3-degree-of-freedom flexible manipulator that moves in a plane can be used to realize simple object handling functions. Most of these mobile manipulators have single functions and limited operating space, and it is difficult for the manipulator to function when the mobile platform is fixed.

The motion accuracy of the manipulator is generally better than that of the mobile platform. Therefore, if the target is within the working space of the manipulator, the task can be completed only by operating the manipulator. This requires the manipulator to have a complex structure and rich functions. A simple idea is to combine mature industrial manipulator products with mobile platforms. The mobile manipulator adopted by N.Xi et al. (J.D.Tan, and N.Xi, Unified model approach for planning and control of mobile manipulators.Proceedings of the 2001 IEEE International Conference on Robotics and Automation, 2001, 3: 3145-3152) is composed of industrial manipulators Puma560 is fixed on the omni-directional mobile platform. A comprehensive The mobile platform and the manipulator with 7 degrees of freedom constitute the mobile manipulator. Kim et al. (Kim, etc.Visualsensing and recognition of welding environment for intelligentshipyard welding robots.IEEE Int.Conf.on Intelligent Robots and Systems, 2000, 3:2159-2165) applied this similar system to the hull of large ships In terms of construction, a three-dimensional structured light sensor is installed at the end of the manipulator to realize trajectory identification and tracking. The above method has fully realized the mobile operation function of the mobile manipulator due to the adoption of mature industrial manipulator technology. But there are also some problems: no suitable installation position for the vision system can be found on the mobile platform, either the viewing angle is blocked by the manipulator, or it conflicts with the workspace of the manipulator. Without a vision system, it is difficult to achieve accurate positioning of the mobile manipulator. Global positioning, if the vision system is installed at the end of the manipulator, it will greatly limit the viewing angle and function of the vision system; the industrial manipulator has a large mass and fast movement speed, and a large coupling force will be generated during the movement to act on the mobile platform On the other hand, it will affect the stability of the platform and easily cause the platform to vibrate or tip over; the energy consumption of industrial manipulators is very large, which is the main burden of the vehicle-mounted energy of the mobile platform.

Contents of the invention

The purpose of the present invention is to provide a mobile manipulator system, which realizes the function of mobile operation through the coordinated control of the manipulator and the mobile platform.

To achieve the above purpose, a mobile manipulator system includes a 3-degree-of-freedom mobile platform, a 5-degree-of-freedom manipulator, and a camera installed on the top of the linear guide rail 5 of the manipulator.

The mobile manipulator is composed of a 3-degree-of-freedom omni-directional mobile platform and a 5-degree-of-freedom manipulator, which can realize a wide range of mobile operation functions, such as moving and transferring files between offices, operating the elevator buttons to make the robot move between floors, etc. A camera with rotation and tilt functions is used and installed on the top of the linear guide rail. The observation of the surrounding scenery can be realized through the high-precision rotation of the camera when the mobile platform does not move. When the manipulator is in a low working position, the camera can be controlled to look down to ensure that the end of the manipulator is within the viewing angle of the camera.

Description of drawings

Fig. 1 is a structural diagram of the mobile manipulator system of the present invention;

Fig. 2 is a plan view of the initial reset state of the mobile manipulator of the present invention.

Detailed ways

The three degrees of freedom of the mobile platform refer to its three motion forms of front and rear, left and right, and rotation on the plane, which can realize all-round movement on the plane, especially in a narrow space, and can move freely. Therefore, it can ensure that the robot arm Operate in a favorable orientation. In addition to wheels, motors, drivers and drive power, the mobile platform also includes ultrasonic sensors and infrared sensors, etc., which can be used to achieve preliminary positioning of the mobile platform.

The manipulator consists of the following parts: torso, shoulder, upper arm, forearm, wrist, and hand. And the joints connecting each part, including 1 moving joint, such as the up and down movement of the slider on the linear guide rail (trunk), and 4 rotating joints such as shoulder joint, elbow joint, wrist rotation joint and wrist swing joint, a total of 5 degrees of freedom. Through the coordinated movement of each joint, the end of the manipulator (hand) can be controlled to move to a designated position, realizing the functions of grasping and manipulation. When the mobile platform moves towards the target in a large range, each connecting rod of the manipulator should be in the initial reset position, and each part of it should not exceed the mobile platform to avoid collision with the external environment. During the movement of the mobile platform, the vision system locates the object to be operated. If the object is within the operating space of the manipulator, the manipulator starts to move to perform the task. If the task cannot be effectively completed by the movement of the manipulator alone, the mobile platform is controlled to coordinate the movement.

Another important part to complete the mobile operation is the vision system, which is installed on the torso of the manipulator to capture images of the external environment, obtain the position information of the object to be operated through image processing, and provide it to the control system of the mobile manipulator as an output control basis for the action.

The present invention will be further described below in conjunction with the accompanying drawings.

The all-round mobile platform 6 can realize the movement of three degrees of freedom on the plane, forward and backward, left and right, and rotation. Ultrasonic sensors, infrared sensors, etc. are installed around the mobile platform 6 to detect external environmental information and realize the movement of the mobile platform. Motion planning, obstacle avoidance and other functions. Considering the structure and kinematic characteristics of the mobile platform during the design process of the manipulator, the combination of the mobile joint and the rotary joint is introduced, which is one of the main features of the present invention. Since the shoulder and elbow joints of the manipulator rotate around the vertical axis in the horizontal plane, it is ensured that the viewing angle of the camera 9 is not blocked by the manipulator, so that the end pose of the manipulator can be accurately judged by the vision system when the manipulator is operating. As the trunk of the manipulator, the guide rail slider 4 can move up and down on the linear guide rail 5 . At the same time, the linear guide rail 5 can be used as a support for the camera 9, so that the position of the camera 9 is fixed relative to the mobile platform 6, which avoids the impact on the positioning accuracy due to the limited viewing angle and motion vibration when the vision system is installed at the end of the manipulator. . The shoulder 3 is fixed on the guide rail slide block 4, and the junction of the upper arm 2 and the shoulder 3 is a shoulder joint, so that the upper arm 2 can rotate around a vertical axis in a horizontal plane. If the distance between the shoulder joint and the center of rotation of the mobile platform 6 is equal to zero, then the degree of freedom of rotation of the mobile platform 6 coincides with the degree of freedom of rotation of the shoulder joint, and a singular phenomenon occurs. However, in this design scheme, the center of the linear guide rail 5 coincides with the rotation center of the mobile platform 6, and the distance between the shoulder joint and the center of the linear guide rail 5 is greater than zero, thereby avoiding the strange phenomenon. The connection between the forearm 1 and the upper arm 2 is an elbow joint, so that the forearm 1 can also rotate around the vertical axis in the horizontal plane. The junction of the forearm 1 and the wrist 8 is the wrist autorotation joint, and its rotation axis direction is consistent with the axial direction of the forearm 1 and perpendicular to the axial direction of the shoulder and elbow joints. The junction of the wrist 8 and the hand 7 is the wrist swing joint, and its rotation axis is perpendicular to the axial direction of the wrist rotation joint. When the rotation angle of the wrist is zero, the shoulder and elbow joints are parallel to the axis of the wrist swing joint. The posture of the manipulator shown in Figure 1 is that the wrist rotation joint has rotated 90 degrees, and the wrist swing joint has rotated 45 degrees.

If the wrist rotation joint angle of the manipulator is fixed to zero, the manipulator is equivalent to a typical SCARA manipulator, including 1 degree of freedom for up and down movement and 3 degrees of freedom for rotation around the vertical axis in the horizontal plane. The forward working space of the manipulator can reach the maximum cylindrical space with the shoulder joint as the axis, the length of the arm as the radius, and the motion stroke of the slider 4 as the height. SCARA manipulators are widely used in the grasping operation of assembly line products. Its main advantages include: the rotation of the mobile manipulator on the horizontal plane can avoid the effect of gravity on the manipulator, effectively reduce motion vibration, obtain high positioning accuracy and ideal mechanical Manual dynamics; also do not need a large power and torque drive motor, reducing the quality of the motor and the quality of the arm, and the quality of the entire manipulator, reducing the burden on the mobile platform 6 driving energy.

If the wrist rotation joint angle of the manipulator changes, the cooperation with the wrist swing joint can change the posture of the end of the manipulator, not limited to horizontal orientation, so it can operate objects whose surface direction is not vertical with a more suitable posture, such as pressing the horizontal plane Buttons on the phone, shaking hands with people, etc. The fine adjustment of the operating height can also be realized without driving the slider 4 to adjust the height of the manipulator, which effectively reduces the consumption of driving energy.

Reset to the initial state when the manipulator is not working, as shown in Figure 2, the whole manipulator is retracted in the mobile platform 6, which facilitates the rapid movement of the mobile platform 6 towards the distant target without making the manipulator collide with the external environment. Wherein the upper arm 2 is rotated to a position perpendicular to the forward direction, and the length of the upper arm 2 is less than the radius of the mobile platform 6, so that any part of the upper arm 2 is in the platform when the reset position is guaranteed. Forearm 1 contracts to the maximum position that does not collide with upper arm 2, and the length of forearm 1 is greater than upper arm 2 length, and is the longest in several connecting rods of arm, and the length of forearm 1 and elbow does not exceed mobile platform 6. The rotation angle of the wrist 8 is zero, and the hand 7 is also retracted to the maximum position where different wrists 8 collide. The length of the hand can vary in a wide range, so as to meet the standard of not exceeding the mobile platform 6 when retracting. The length of each connecting rod is substantially equivalent to the arm size of a human body.

The visual system adopts a camera 9 with rotation and pitch functions. The observation of the surrounding scenery can be realized through the high-precision rotation of the camera 9 when the mobile platform 6 does not move. When the manipulator is in a low working position, the camera 9 can be controlled to look down to ensure that the end of the manipulator is within the viewing angle range of the camera 9 . If the global positioning is carried out by the ceiling lights, the elevation angle of the camera 9 can also be controlled to take images in front of the mobile manipulator.

The computer control system is installed inside the mobile platform to process ultrasonic and infrared sensor signals, and visual image processing, calculate the position of the target, and output control commands for the coordinated movement of the mobile platform and the manipulator, so that it can effectively complete the movement function of the operation.

The display 11 of the computer control system is installed on the back of the manipulator, and can be used to display the dynamic images captured by the camera 9, and the position information of the mobile platform in the entire environment, etc., so as to facilitate the monitoring and debugging of the entire system by operators.

Claims (9)

1. A mobile manipulator system, including a 3-degree-of-freedom omnidirectional mobile platform, a 5-degree-of-freedom manipulator, a vision system and a computer control system. 2. The system according to claim 1, wherein the mobile platform is a 3-degree-of-freedom omnidirectional mobile platform, and ultrasonic and infrared sensors for detecting environmental information are installed on the mobile platform. 3. The system according to claim 1, wherein said manipulator comprises 1 moving joint and 4 rotating joints. 4. The system according to claim 3, characterized in that the up and down moving joint is composed of a linear guide rail (5) and a guide rail slide block (4). 5. The system of claim 3, wherein said four rotational joints include shoulder joints, elbow joints, wrist autorotation joints and wrist swing joints. 6. The system according to claim 1, wherein the center of the linear guide rail (5) coincides with the center of rotation of the mobile platform (6), and the distance between the shoulder joint of the manipulator and the center of rotation of the mobile platform (6) is greater than zero. 7. The system according to claim 1, characterized in that said camera is a camera with rotation and tilt functions. 8. The system according to claim 1, characterized in that the manipulator is located in the mobile platform (6) in the initial state. 9. The system according to claim 1, characterized in that the computer control system installed inside the mobile platform realizes digital signal processing and control command output, and controls the mobile manipulator to complete the mobile operation.

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