RITA - Development

RITA - Development

The meaning of the acronym RITA is “Robot with Integrated Tacheometer steering for different Applications”. This robot is developed as a quasi-autonomous robot for various surveying purposes. Different challenges have to be met. The system should always be intuitive to use, deliver results in real time, improve working conditions (such as continuous stooping), and complete the measurement task in a significantly shorter time than usual. As a quasi-autonomous robot for the height control of floors, additional attention must be paid to the height accuracy to be achieved. On the other hand, as a stakeout robot, a high level of position accuracy must be achieved.

Motivation

The robot for height control of hall floors was developed as part of a ZIM project.
Up to now, the height control of hall floors according to DIN 18202:2019 is carried out by leveling a previously tachymetrically marked grid (1m x 1m). The result of our ZIM project "Development of a mobile robot for height control of floors" should be a rather-autonomous robot that performs the task in less than 20% of the usually necessary time (10 s/point incl. travel time) with significantly reduced manpower. A further time saving by factor of 4 results compared to leveling.

RITA

As a preliminary study of the project, a rather-autonomous robot (RITA, Robot with Integrated Tacheometer steering for different Applications) was developed as a functional model with the aim of approaching points without maneuvering in order to enable line-shaped markings in the future. In the first phase, the robot carries a triangulation sensor to determine the distance between its polar (tacheometric) reflector and the ground. Development requirements are:

• 0.3 mm height, 2 mm position
• modifiable to 0.1 mm position (marking)
• Set-up time < 30 min
• Can be put into operation by technician
• Autonomous processing of the measuring task
• Battery operation time at least 4 h (battery system of the robot is identical to that of the measuring devices)
• Suitable for on-board luggage (mass of the vehicle approx. 8 kg)

Regular test runs support the continuous further development, so that the development specifications stated above are partly significantly exceeded. You can see an impression of the motion sequence in the following video.

Videoimpression

Scientific-technical Challenges

In order to minimize the inclination of the vehicle during braking and the resulting positioning errors, a gimbal-mounted pendulum, which is damped analogously to the driving process and carries both the reflector and the triangulation sensor, is integrated. In this context, the mechanical coupling for reflector tracking (orientation to the tachymeter [1] in each driving direction) represents an additional challenge. In order to ensure a target-optimized approach even in the case of uneven ground, a special drive solution was developed that enables low-backlash power transmission and thus increases directional stability during travel, as shown in the following chart. The positioning of the car without maneuvering will be performed by a Bayesian-based navigation solution integrating multisensor fusion [2]. In respect of the current state of knowledge, integrating a laser tracker will be required. Due to the high data rate when using a laser tracker instead of a tachymeter, WLAN is unsuitable and therefore the implementation of an optimized radio system was will be required.

Acknowledgments

Especially the development of the pendulum and the Bayesian-based navigation solution is funded by promotion-project ZIM under contract No. ZF4470901, launchend by the German Federal Ministry of Economic Affairs and Energy (BMWi). The project includes a coporation with surveyor's office Lingel, Aalen.

Literature

[1] BERTELS, M. [2018]: Evaluierung der Leistungsfähigkeit einer Roboter-Totalstation zur Objektverfolgung in Echtzeit, Bachelorarbeit, GIK, unveröffentlicht.

[2] ULRICH, T. [2016]: Uncertainty Modelling of High-precision Trajectories for Industrial Real-time Measurement Applications. Dissertation, 81 S. + Anhang. KIT. URN: urn:nbn:de:swb:90-604401, KITopen ID: 1000060440.

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