Continuum robots are considered one of the most exciting kinds of robotics technology of our time. Their continuously changeable structure opens up new usage possibilities – for example in medical technology, for inspections in confined spaces or in human-robot interactions critical to safety. At the same time, they pose enormous challenges when it comes to research and development, especially for modelling, state estimation and control.
This very challenge was addressed in an ongoing research project at the Faculty of Control Engineering at the Technical University of Munich (TUM). The goal was to build a cable-actuated continuum manipulator that allows tendon forces to be measured with high precision and directly controlled, as a basis for novel model-based control and observer concepts. This is where the innovative SensoJoints from Sensodrive came into play.
An experimental robot for gaining new scientific insights
The project focused on the development of an experimental robot system with a flexible backbone and cable-based actuation. Unlike classic industrial robots, a continuum robot does not have distinct joints, but continuously changes shape along its entire length. Movement is generated via several tendons and their tension must be specifically adjusted.
For research, this means:
only if the output torques and forces can be precisely measured and controlled can realistic models be validated, states reliably estimated and external disturbances detected. This precisely describes the limitations of the drive solutions used previously, as they only allowed indirect torque control via motor currents.
Why SensoJoints played a key enabling role
For the new experimental setup, the TUM research team purposefully chose SensoJoints from Sensodrive. The decisive factor was the overall package on offer, consisting of direct, high-resolution torque measurement, powerful advanced torque control and open, transparent system architecture.
Only through direct controlling the output torque – including compensation for gear effects such as friction or ripple – could the continuum robot be set up and used productively so quickly. Instead of designing their own drive solutions with high development costs, the team had access to market-leading technology that was immediately usable.
Another success factor was seamless integration: thanks to the comprehensive documentation and the fact that common standards such as CiA402 were supported, it was possible to prep hardware and software even before delivery. This significantly reduced the time from planning to setup.
Precise measurement data as the basis for research at the highest level
The added value of SensoJoints became clearly evident in operation. The precise torque measurement on the output side enabled an analysis of the system's behaviour that was previously unattainable. At the same time, effects that distorted previous experimental setups – such as uncompensated gear friction – could be effectively eliminated.
The experimental data obtained in this way formed the basis for the validation of new discrete modelling and observer approaches and were directly incorporated into a scientific publication. This turned the continuum robot into not just an experimental setup, but a reliable reference system for further research.
Partnership on equal terms
In addition to technology, teamwork also played a key role. The TUM team found the technical advice, accessibility and exceptionally transparent documentation particularly worthy of note. Instead of a black-box solution, a system was available with behaviour that could be traced in detail and purposefully used – a crucial advantage in a scientific context.
From the project managers' point of view, Sensodrive's genuine interest in the research topic was a particular highlight of the collaboration. Solutions were not "sold", but developed together, with the clear goal of creating the best possible technical basis for research.
Future outlook: From modelling to control
Following successful work on model identification and state estimation, the project's focus is now increasingly shifting towards model-based control of the continuum robot. SensoJoints will continue to play a central role.
The project impressively demonstrates how complex research platforms can be realized in a very short time using off-the-shelf, torque-controlled drives without compromising on precision or quality. For Sensodrive, the collaboration with the Technical University of Munich is another example of how SensoJoints, as core technology, enable innovative robotics research.
More information about the innovative SensoJoints
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