- The paper demonstrates a cost-effective design of Stretch that integrates a two-wheeled base, lift, and telescoping arm for effective indoor manipulation.
- It details a novel wrist mechanism enabling dual operation modes, including stowing and tool deployment for tasks like grasping and handovers.
- Empirical tests and stability models, grounded in anthropometric data, validate its performance for domestic assistive applications.
Design of Stretch: A Mobile Manipulator for Indoor Environments
The paper presents the design and development of "Stretch," a compact, lightweight mobile manipulator tailored for tasks in indoor human environments, with an emphasis on reducing size, weight, and cost while maintaining performance capabilities. The research delineates the challenges and solutions associated with developing a mobile manipulator suitable for applications such as assistive technologies and domestic service within constrained settings prevalent in homes and offices.
Core Design and Functional Components
Stretch's design consists of a two-wheeled differential-drive mobile base, a lift, and a telescoping arm engineered to facilitate Cartesian movement at the end of the arm. The mobility is enabled through four main actuators: two for the wheels, one for vertical arm lift, and another for extension and retraction of the telescoping arm. This configuration reduces the complexity and cost while supporting essential manipulative tasks and movement.
An innovative feature of Stretch is its wrist mechanism, which incorporates a wrist yaw joint, enabling stowing and deployment of tools within the footprint of the base. This supports the dual modes of operation: navigation mode and manipulation mode, allowing tasks like handovers, object grasping, and utilizing drawers.
Anthropometrical and Structural Insights
The design leverages anthropometric data to match Stretch's dimensions to typical human activities and spatial constraints. For instance, its narrow width of 34 cm matches the average hip width of adults, and its arm reach of 71 cm aligns with human arm length. The camera's vertical placement reflects human eye levels for enhanced perception and interaction capabilities.
Empirical and Mathematical Validation
Stretch's performance and stability were assessed through mechanical models and empirical testing. Static stability analysis demonstrated tradeoffs between robot dimensions and functional capabilities, setting benchmarks for payload capacity and operational forces. For instance, the maximum payload is modeled as inversely proportional to the arm reach, emphasizing the delicate balance between compact form and functional reach. Empirical tests corroborated the model predictions, confirming that Stretch can perform various household tasks autonomously or via teleoperation.
Practical Implications and Future Directions
Stretch's design offers significant benefits by catering to a growing need for assistive and service robots in personal and professional spaces. Its commercial availability as the Stretch RE1 marks a shift towards wider adoption of mobile manipulators, supported by its lower cost compared to comparable models. Future developments may focus on enhancing autonomous task execution and refining user interfaces to integrate seamlessly within diverse human-centric environments.
In conclusion, the paper presents a thorough exploration and justification of Stretch’s design, illustrating its potential to contribute meaningfully to domestic robotics' advancing landscape.