Contents lists available at ScienceDirect Automation in Construction journal homepage: www.elsevier.com/locate/autcon Glass facade cleaning robot with passive suction cups and self-locking trapezoidal lead screw drive Thein Than Tun a, ⁎ , Mohan Rajesh Elara b , Manivannan Kalimuthu c , Ayyalusami Vengadesh a a Temasek Laboratories, Singapore University of Technology and Design, Singapore b Engineering Product Development, Singapore University of Technology and Design, Singapore c Nanyang Technological University, Singapore ARTICLE INFO Keywords: Climbing robot Self-locking lead screw Passive suction cups ABSTRACT We report on the mechanism, design iteration, and performance of a new glass facade cleaning robot, vSlider. The passive suction cups, driven by self-locking lead screws, are used to engage the vSlider robot to the glass facade. This mechanism has higher efficiency, compared to active suction cups, and offers better power consumption and safety in the case of power disruption or power loss. Due to the self-locking leadscrews, the counter-moment in a static position is not transferred to the motor, and thus, the servos which drive the lead screws only consume the power needed for a typical free load. A DC motor with encoder generates the primary locomotion in vSlider which was tested both in position- and velocity-control modes. This paper also details the design iteration efforts and discusses the key findings from the experiments involving the first prototype, vSlider 1.x, and the application of these findings in the development of the second prototype, vSlider 2.x. Experiments were performed to va- lidate the proposed design approach and to benchmark the performance of the two robot prototypes that were developed. 1. Introduction Glass facade cleaning robots are fast becoming one of the key re- search topics within the robotic field. The need is mainly attributed to many high-rise glass facade buildings along with the advancement in the architecture. Environmental concerns, including a move to sus- tainable buildings, is the motivating factor behind developing glass- facade high-rise buildings due to the attractive properties of glass such as transparency, workability, 100% recyclability, resistance to corro- sion, and energy efficiency, among others. The enormous technical advancements in the building and construction industry are increas- ingly transforming the form of modern high-rise buildings. Many con- temporary high-rise buildings are characterized by large-area glass fa- cades [1]. Hence, the need for maintaining such buildings and servicing new ones that are yet to be built has significantly increased. Currently, almost all maintenance works are performed by manual labor, where safety, cost and cleaning efficiency are of great concern. Driven by additional factors such as labor shortage, immigration policies, and productivity drives, there has been a recent trend in developing and deploying robotic systems for cleaning glass facades in such buildings. RobuGlass presented in [2] was designed for cleaning the Paris museum known as the Louvre Pyramid which is 21 m high and inclined by 50 degrees. The device has four caterpillar tracks for locomotion and eight vacuum pumped-suction cups to engage to the glass panels. This 55 kg robotic system also has a rotating brush and wiper for cleaning purpose, and the overall dimensions are 1200 × 900 mm. Another robotic system with similar features is SkyBoy, designed for cleaning the glass facade of the control tower at the Guangzhou Airport, Guangzhou, China [3]. This robotic system consists of a cleaning robot and a conveyor system which is composed of a top dolly and a bottom dolly. The cleaning robot is driven up and down by the conveyor system where the top and bottom dollies orbit around the cone-shaped struc- ture tower with similar angular velocities. Moreover, to simplify the robot design process for cleaning the four floors of the tower, the in- dividual SkyBoy system is deployed on each floor rather than one system which can climb over the stainless-steel ring on each floor. Another robot platform that requires support from operating infra- structure was developed by the Fraunhofer Institute of Manufacturing Engineering and Automation (IPA)[4]. The system is known as the Standard Facade Cleaning Robot (SFR I) and the iterated design (SRF II) has three degrees of freedom to move up and down, left and right, and to overcome the standard facade frame. The additional units, such as the supply unit and control unit, are located on the ground floor. Moreover, the Fraunhofer Institute for Factory Operation and https://doi.org/10.1016/j.autcon.2018.09.006 Received 14 August 2017; Received in revised form 23 August 2018; Accepted 11 September 2018 ⁎ Corresponding author at: 8 Somapah Rd, 487372, Singapore. E-mail address: thantun_thein@sutd.edu.sg (T.T. Tun). Automation in Construction 96 (2018) 180–188 0926-5805/ © 2018 Elsevier B.V. All rights reserved. T