Mobile-manipulator systems (MMS) are extremely useful tools in teleoperation tasks. However, the current command strategy is strenuous and difficult and requires extensive training. A new command strategy is presented where control of the entire MMS is done using a single joystick. Rather than modeling the system as a redundant manipulator, control of the manipulator and mobile base is decoupled. In two separate states, the operator either controls the manipulator or the base. The system automatically switches between states based on the configuration of the manipulator. Testing is performed using the Omnibot MMS, a holonomic platform with a 3-DOF manipulator. The results showed that less time is required for completion of the tasks. In addition, the tasks are completed with greater accuracy and lower power consumption. Operators who used the system agreed the new command strategy was easier and more intuitive.
In this work a novel command strategy is presented for tele-operating a mobile-manipulator system. To test its effectiveness, the command strategy was implemented on the mobile-manipulator system “Omnibot MMS”. The Omnibot MMS is teleoperated using a three degree-of-freedom haptic joystick and is controlled by driving either the base or the manipulator using an intuitive automatic mode switching command strategy. Virtual fixtures are used to provide additional information to the operator about the configuration of the Omnibot MMS, as well as increase accuracy and decrease errors. Through testing it was shown that new operators increased performance faster using the novel command strategy, and both accuracy and efficiency were improved, when compared to the traditional method of control using two joysticks.
This paper presents the results of shotcrete thickness estimation for mining applications using a mobile robot. The method uses a fiducial marker based registration method to align initial and posterior LIDAR scans. The shotcrete thickness was calculated using point to point estimation. The registration and thickness estimation were tested in a mock mine using a LIDAR scanner on a mobile robot. It was found that the registration based thickness estimates had repeatability within a millimeter when compared to thickness estimates generated without the need for registration.
Tele-operation of mobile-manipulator systems (MMS) is typically done by modeling both the manipulator and mobile base as a single system combined with the use of various redundancy resolution techniques to achieve coordinated motion. In this work, the Omnibot MMS is controlled by a 3-DOF (degrees-of-freedom) haptic joystick. The base is a holonomic platform having 3-DOF supporting a 3-DOF manipulator capable of position control within its workspace. By controlling the base and manipulator individually, redundancy resolution techniques are not required because the master has equal DOF to the device it is controlling at any given time. Two command strategies are proposed herein for automatic switching of control between the manipulator and base. The first command strategy is a virtual wall method that uses haptic forces to make the operator feel like they are pushing against a wall at the edge of the manipulator’s workspace, resulting in the base moving. The second command strategy is a two state approach in which each state controls a different device and switching between the two is done by breaking through the workspace limits. With the help of haptic forces, the operator has the sensation of breaking through a compliant surface when switching states. The two proposed strategies were implemented and tested on the Omnibot MMS and both subjective and objective data was used to evaluate and compare the two methods.
SUMMARY This work presents a novel command strategy developed to improve operator performance and minimize difficulties in teleoperation tasks for mobile-manipulator systems with a holonomic base. Aimed specifically at novice operators, virtual fixtures are introduced as a means to minimize collisions and assist in navigation. Using the 6-degree-of-freedom (DOF) Omnibot mobile-manipulator system (MMS), a command strategy is implemented such that the operator need only control a 3-DOF haptic joystick to achieve full control of the Omnibot MMS. The command strategy is used to coordinate control between the arm and the base of the system, prevent collisions with known obstacles, and alert the operator of proximity to those obstacles with haptic forces. Through experimental testing it is shown that operator performance improved with the use of virtual fixtures.
In this work, an approach to generating a set of via points for use in manipulator trajectory path planning is presented. The approach was developed for use on a robotic underground mining system, particularly for the task of autonomous application of a sprayable concrete called shotcrete. A LiDAR (light detection and ranging) scanner on a nodding head produces point clouds that are used as the input for the via-point selection algorithm. The algorithm generates a set of position and orientation via points that the manipulator must follow to perform the shotcreting task. The developed algorithm has been successfully tested on an autonomous mobile-manipulator system in a scaled mock-up of an underground mine. The main advantage of this algorithm is the ability to generate via points for any section of an underground mine in any position relative to the robot.
