Physical prototype of QM-REX

Project Motivation

Many construction tasks are laborious and manpower intensive. For example, installation of a structural, mechanical, or architectural element may require several workers to carry the workpiece to a designated location, lift it into position, and hold it steady while other workers secure the workpiece in place. As a result, the installation of even a simple element may require several workers, is time-consuming, and prone to error which results in the need to repeat the work. This is a cause of low productivity for many tasks in the construction sector.

Moreover, many construction tasks pose high risk of physical injury to construction workers. Compared to all other sectors, construction has the highest injury rate which averages around 17% from 2016 to 2018. One of the most common accidents is falling from heights when working on a ladder, of which more than 400 cases were reported in 2017. Such accidents typically occur when workers need to carry and install bulky objects while standing on a ladder. Without being able to maintain a three-point contact while using ladders, workers can easily lose their balance when performing installation tasks.

Therefore, in line with the Building and Construction Authority’s push for adoption of innovative technologies to improve productivity and safety in the construction section, this project aims to design a user-friendly means to assist construction workers to perform works at height while handling objects in a safe and productive way.

Design

The proposed solution, QM-REX, is a portable machine that comprises a semi-intelligent arm manipulator that is mounted on an elevating platform. The machine is designed to carry a workpiece to a desired location and hold it stationary while a single worker installs it into position by standing on a stable platform. The solution also eliminates the need for extra workers to hold the workpiece while it is being installed. Hence, QM-REX is designed to increase productivity and safety of installation tasks at height through its single-worker plus hands-free operation.

The arm manipulator consists of a 0.5 m long upper arm that is connected to a 0.5 m long forearm via an elbow joint which is actuated using a stepper motor plus pulley belt mechanism to generate the required torque. The end effector, which is designed to hold a workpiece, is attached to the forearm through a wrist that is driven by a servo motor. The entire arm is attached to a 1 m long linear actuator via a shoulder joint which turns the upper arm using a stepper motor. The linear actuator allows the entire arm to be moved vertically in order to position the workpiece. The movement of the arm and linear actuator is designed to be operated in a coordinated manner by a user via an intuitive control panel.

In order to use proposed solution, a worker would first maneuver QM-REX to the location where an installation work needs to be done. Then, the worker would press a button on the control panel to reset the arm manipulator. Next, another button would be pressed to activate the arm in loading position after which the worker can place the workpiece on the end effector. Subsequently, the worker may get on the elevating platform and use the control plane to raise the arm and himself to an appropriate height before by using the arm to place the workpiece in position by pressing the relevant buttons on the control panel. Once the workpiece is in place, the worker can install the workpiece without having to hold on to it.

A physical prototype of QM-REX’s arm manipulator was made to showcase its range of motion and size of working area for a worker. Preliminary tests on the prototype showed that the arm manipulator plus linear actuator was able to lift workpieces that weighed up to 1 kg and measured up to 0.8 m × 0.8 m to a maximum height of 2 m from the ground. The workpieces could be placed at their desired position with a resolution of 5 mm. The average time taken to get a workpiece in position after it was placed on the end effector was around 1 minute. Thus, it is envisioned that QM-REX has a significant potential to improve productivity and safety of installation tasks at height through its single-worker plus hands-free operation.