Robotic Arm for Confined Space Construction Tasks
Automation & Robotics for Construction
Challenge Statement Owner
Obayashi Corporation is one of the leading general contractors in Japan and has been operating in Singapore since 1965. The company is renowned for its large-scale civil engineering projects and the creation of iconic architectural masterpieces. It is committed to technological innovation and sustainability, contributing to the development of a safe and prosperous society.
Background
In construction, confined spaces such as pits beneath manholes present significant hazards when using conventional methods. Tasks like grinding, chipping, waterproof coating, and painting generate dust and fumes, while waterproofing coatings can release volatile solvents. Workers often operate in positions where standing is impossible, relying on masks and temporary lighting, while monitoring oxygen levels. These conditions expose workers to physical strain, toxic fumes, dust, low oxygen, and other safety risks.
There is strong demand for robots to replace tasks in confined spaces. These tasks require robots with a high degree of freedom (DOF) to move in multiple directions and angles, adjusting movements to avoid obstacles and reach work positions. Tasks include grinding, cleaning, chipping, waterproof coating, and painting. Waterproofing may be prioritised, because it is easier to execute with a robotic solution and workers can reduce their exposure to toxic air. Waterproofing workflows typically involve multiple sequential steps that require workers to enter the tank through the manhole: surface cleaning and preparation (including plastering, if required), application of primer, multiple layers of waterproofing coating, reinforcement (if required), and finally final coating.
Currently, there are no robotic execution solutions for these tasks; available robotics in this space are limited to inspection drones. Existing robotic designs are often too large for the tight dimensions of confined spaces, and must be downsized or made modular to enable access and manoeuvrability.
The Challenge
How might we automate construction tasks in confined spaces using a modular, robotic arm that is capable of performing waterproofing, coating, and other surface preparation tasks?
Requirements
Functional Requirements
- Perform tasks without a person entering the confined space
- Operate via remote control or autonomously, with full automation as a future goal
- Installable from outside, including at manhole entrances
- Monitor the work process and generate construction records, including visual inspection and material application path/usage tracking
- Capable of grinding, cleaning, and waterproofing coating inside the space (surface cleaning and preparations, and chipping are optional)
- Fit and be positioned at manhole entrances, reaching around beams and obstacles
- Access all six surfaces of a pit measuring approximately 6m x 2-3m x 3-4m
- Be lightweight and portable – ideally under 50kg, or modular (e.g. 4 x 25kg) for portability
- Operate in poor lighting, with dust and fume exposure; dust extraction capability preferred
Technical Requirements
Core Requirements:
- High DOF robotic arm with multiple joints for flexibility and obstacle avoidance
- Reliable real-time data transmission and communication in underground, concrete-surrounded locations
- User-friendly control interface and advanced algorithms for precise control of high DOF robots
- Stability mechanisms for base, arm, and end effector to maintain precision in operations like grinding, chiselling, waterproofing, and coating
- Simple design for ease of mass production at cost lower than an industrial robotic arm with mobility system
Additional Preferences:
- Long-reach robotic arm suspended from above the manhole
- Modular components for task flexibility
- Durable against dust, vibration, and solvent exposure
- Capability to operate continuously (24/7) to offset slower task speeds
Expected Outcomes
- Elimination of the need for workers to enter hazardous confined spaces
- Reduction of safety risks from dust, solvent exposure, oxygen deficiency, and awkward postures
- Up to 50% manpower reduction for waterproofing operations
- Increased task efficiency and continuous operation
Deployment Environment and Constraints
The robot will be deployed in confined space works such as pits beneath manholes. It must be installable from outside, manoeuvrable within spaces approximately 6m x 2-3m x 3-4m, and able to reach around beams, manholes, and other obstacles. It must maintain communication and control in underground, concrete-surrounded conditions and withstand dust, fumes, low oxygen, and poor lighting.
Proof-of-concept (POC)/Pilot Support
Obayashi proposes conducting the POC by installing a mock-up at the BCA Braddell Campus, with the scope of work clearly defined before development. Upon successful completion, a site for field testing will be selected based on project timelines, with the possibility of testing at a site in Japan.
Evaluation metrics will include safety (eliminating the need for human entry) and productivity (ability to operate continuously, even 24/7).
Obayashi will provide:
- Installation and logistics support for setting up the robotic system
- Subject matter expert input from safety, engineering, and site operations teams to refine design and functionality
- Real-world environmental parameters (e.g., pit layouts, beam and obstacle locations, lighting and ventilation conditions) to inform system design
- Regular feedback through structured project review meetings, including performance evaluation against safety and productivity metrics
Commercialisation and Scaling
If proven effective, the robotic solution will be adopted in Singapore projects, with potential support for commercialisation in Japan to expand the market. Its design flexibility could enable application in a variety of construction tasks beyond confined spaces, including interior and other restricted-access environments.
