Patent Publication Number: US-2021180351-A1

Title: System and method for building façade cleaning and painting with a dual cable-driven robot

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority from the U.S. provisional patent application Ser. No. 62/948,778 filed Dec. 16, 2019, and the disclosure of which is incorporated herein by reference in its entirety. 
    
    
     FIELD OF THE INVENTION 
     The present invention pertains to a robot system for building façade maintenance operations. More particularly, the robot system includes a platform including one or more robot arms installed on the platform for windows and/or facade cleaning, maintenance, and painting using plural tools. 
     BACKGROUND 
     Exterior façade operations, such as window cleaning and painting, have been identified by the construction industry as expensive and dangerous. For high-rise buildings having over 30 floors, the most common approach is to employ rope or gondola-based systems, either by restraining a worker using ropes/cables or restraining the platform in which the worker(s) stand on to perform the required tasks. Due to the difficulties in entering and leaving the system, the laborers are typically working for extended periods of time. Additionally, at such high working heights, the harsh weather conditions, high heat, wind and rain, also cannot be avoided. Furthermore, cases of accidents, although infrequent, will typically result in either serious injury or death to the workers. These factors have resulted in a lack of skilled workers, increasing worker insurance costs and consequently high labor costs. 
     To address these concerns, robots have been developed to automate specific façade maintenance operations and replace the more dangerous work performed by humans. Window cleaning robots are amongst the most common that have been developed for exterior façade work. The most common type of robot that is used is a mobile robot, where the mechanism typically either crawls or use wheels to maneuver, and is secured with a safety harness to prevent the robot from falling and injuring pedestrians below. Another type of application for these mobile robots is the painting of large façades. There are two characteristics that must be noted for such existing façade maintenance solutions. First, the methods typically involve spraying of water or paint, or using rolling brushes. These techniques have not been well accepted by the building industry, for their inability to sufficiently clean or paint building surfaces. Second, such mobile robots only operate well on flat, or close to flat, surfaces and struggle on more complex surfaces or when the building façade has any protruding features such as boxed or bay windows or curved glass walls. Non-flat and surfaces with protruding features are common in many high-rise buildings in Hong Kong, particularly those resulting from modern architectural designs. Thus, there is a need for robotic building façade maintenance systems that can accommodate a wide variety of complex architectural features. 
     SUMMARY OF THE INVENTION 
     Recently, the development of dual cable-driven robot systems has been adapted to autonomously perform window cleaning and façade painting/maintenance. Rather than mobile robots, dual cable-driven robots are a special type of parallel robot where multiple cables are used to drive platforms equipped with robot arms. The primary advantage of dual cable-driven robots compared to mobile robots is that robot arms are mounted on a platform that is securely positioned and controlled, Advantageously, a variety of building façade maintenance tasks may be performed by the robot arms. 
     The inventive system combines the dexterity of robot arms with the dual cable-driven platform&#39;s ability to operate over large areas. Furthermore, the robot arms permit cleaning with wipers and painting with rollers in the same manner as human workers, including the ability to operate on surfaces that are not completely flat. Through the use of a system controller, cooperation between the robot arm(s) and the platform may be coordinated so that any positional aberration in the platform (e.g., tilt, distance from the façade surface, etc.) can be compensated for by the robot arms to ensure accurate cleaning or painting. 
     The present invention pertains to a system comprising a dual cable-driven robot that can be configured to control the position of a working platform. The system also comprises robot arms which can be mounted on top of the working platform. The system is capable of cleaning windows and painting façade. The dual cable-driven robot can be configured to handle different size of building façade. Motors and winches are installed at the ceiling and floor of the façade, which guides and control the cable in which connected to the platform and allows the platform to travel to different position. In one embodiment, the dual cable-driven robot system may be driven by a single motor handling two cables. In this manner, the number of motors necessary to drive the eight cables attached to the platform is reduced, while maintaining the stiffness and increasing the platform stability. 
     One or more robot arms mounted to the platform perform the motions necessary for building maintenance operations. Since the platform remains close to the façade surface, different motions are performed by the robot arm for cleaning and painting. When multiple robot arms are employed, they cooperate for tasks, which improves the working efficiency increases the ability to perform complex tasks. 
     The system of the invention can perform end-to-end windows cleaning and façade painting procedures, including a solution-dispensing system (e.g., paint, cleaning fluid) to robot(s) mounted on the dual cable-driven platform. Through computer control and optional feedback through sensors, building maintenance processes can be automated more than conventional methods and require less human intervention. The system of the present invention has good scalability and portability, and can easily adapt to different façade surfaces building sizes and configurations. As compared to mobile robots, the present robot system simulates human cleaning and painting, improve finishing quality and efficiency. 
     In certain embodiments, the system may include human interactive controls such as joystick or other remote controllers, to control the position of the platform and motion of the robot arm(s) in real time. This is to provide an alternative way to manually control the system when desired. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Some embodiments of the present invention are illustrated examples and are not limited by the figures of the accompanying drawings, in which like references may indicate similar elements and in which: 
         FIG. 1A  illustrates a perspective view of one embodiment of the system of the invention, with a dual cable-driven robot system, a moving platform with robot arms, winch systems and actuators. 
         FIG. 1B  illustrates a side view of an upper cable system used with the platform of  FIG. 1A . 
         FIG. 1C  illustrates a side view of a lower cable system used with the platform of  FIG. 1A . 
         FIG. 2  shows the end-effector platform design of an embodiment of the dual cable-driven robot system, comprising robot arms, a source of power, cable guiding winch system and other components required for the tasks. 
         FIG. 3A  illustrates a single suspension system for the platform of  FIG. 1A . The system includes an overhang beam and set of pulleys.  FIG. 3B  illustrates a cable guiding system for the platform of  FIG. 1A . The system comprises pulleys that used to guide the cable at the floor level. 
         FIG. 4  illustrates a cable actuating unit for the system of  FIG. 1 . 
         FIG. 5A  illustrates a robot arm with window wiper mounted at the tip.  FIG. 5B  is an enlarged view of the end of the robot arm of  FIG. 5A . 
         FIG. 6A  illustrates a robot arm with a sponge roller tool.  FIG. 6B  is an enlarged view of the end of the robot arm of  FIG. 6A . 
         FIG. 7A  illustrates a robot arm with a paint roller mounted at the tip.  FIG. 7B  is an enlarged view of the end of the robot arm of  FIG. 7A . 
     
    
    
     DETAILED DESCRIPTION 
     The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. As used herein, the singular forms “a,” “am,” and “the” are intended to include the plural forms as well as the singular forms, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, steps, operations, elements, and/or components, but do not prelude the presence or addition of one or more other features, steps, operations, elements, components, and/or groups thereof. 
     Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one having ordinary skill in the art to which this invention pertains. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and the present disclosure and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein. 
     In describing the invention, it will be understood that a number of techniques and steps are disclosed. Each of these has individual benefits and each can also be used in conjunction with one or more, or in some cases all, of the other disclosed techniques. Accordingly, for the sake of clarity, this description will refrain from repeating every possible combination of the individual steps in an unnecessary fashion. Nevertheless, the specification and claims should be read with the understanding that such combinations are entirely within the scope of the invention and the claims. 
     Dual cable-driven robot system, apparatuses, and methods for windows cleaning and façade painting in 3D space are disclosed herein. In the following description, for purposes of explanation, numerous specific details are set forth to provide a thorough understanding of the present invention. It will be evident, however, to one skilled in the art that the present invention may be practiced without these specific details. 
     The present disclosure is to be considered as an exemplification of the invention and is not intended to limit the invention to the specific embodiments illustrated by the figures or the description below. 
     The present invention will now be described by referencing the appended figures representing preferred embodiments.  FIG. 1A  depicts an isometric view of the system for building maintenance such as window cleaning and façade painting using a dual cable-driven platform with one or more robot arms. The dual cable robot system includes an end-effector platform  101 , cable winch and actuating unit  102 , system controller, tool changer and consumable refilling station  103  and cable routing suspension systems  104 ,  105 . One or more robot arms  201  are mounted to platform  101 . 
     As seen in  FIG. 1A , the cable routing systems  104  and  105  may be mounted at fixed points on the building or at points adjacent to the building (e.g., lower cable routing system  105  may be mounted permanently or temporarily on the ground in front of the building). The dual cable robot system of the present invention includes independently-drivable cable pairs  122 ,  124 ,  126 , and  128  that used to control the position and tilt of platform  101  by varying the cable length through actuating unit  102 . The term “dual cable” is defined as there are four pairs for a total of eight cables controlling the position of platform  101 ; each set of cables is controlled as a pair. Each cable pair has one end fixed at position  104  or  105 , with the other end connected to the actuator  102 . Note that while a single actuator  102  is depicted, plural actuators may also be used. A pulley system  204  (to be described in more detail below) on the platform  101  enables the platform to be stably positioned by the dual cable configuration. Importantly, by providing a system of four pairs of cables, the positioning may be precisely controlled such that the system can be employed on buildings with irregular facades, for example, boxed windows, bay windows, curved surfaces, and architectural features. 
     To assist with the correct positioning of platform  101  and robot arm(s)  201 , plural positional sensors  109  and/or machine vision elements  110  may be positioned along the platform periphery (e.g., the leading edges of the platform) and on the robot arms. Feedback from the sensors/machine vision elements is used to determine the attitude of the platform (e.g., platform tilt) and can be fed to a system controller. 
     Unit  103  may include a variety of system elements including the system controller along with optional a consumable material reservoir/refilling station and optional tool changing station. The motion of the dual cable actuator  102  is controlled by the system controller in unit  103 , which is responsible for calculating the corresponding cable movement and required cable lengths to drive the platform  101  to the desired work area. Importantly, the controller coordinates the motion of both the robot arm(s) and the platform, optionally in connection with the sensors described above. Through the coordination of platform/robot arm movement, any positional aberration in the platform (e.g., tilt, distance from the façade surface, etc.) can be compensated for by the robot arm to ensure accurate cleaning or painting. 
     In one aspect, the optional sensors  109  and  110  may be used to map the building façade features prior to performing building maintenance operations. By mapping the façade features, the system controller may calculate the trajectory of platform  101  and the position of robot arm(s)  201 . Machine vision elements can determine the position of glass surfaces for window cleaning, and walls for façade cleaning, calculating a path for window cleaning with a window-cleaning tool followed by a path for façade cleaning with a façade-cleaning tool. In this manner, the most efficient path can be calculated for the various maintenance functions to be performed, minimizing the number of tool changes/fluid changes that are needed to perform multiple functions. 
     Tool changing can be performed in an automatic or semi-automatic fashion with a commercial or custom-built tool changing station in unit  103 . Alternatively, a tool-changing station may be included on platform  101  to minimize the distance that platform  101  must travel. Similarly, a material reservoir may be included on platform  101  to minimize the distance needed to supply cleaning or painting material to the vicinity of the robot arm(s). 
     The dual cable robot system works in a planar workspace and the cable configurations can be viewed as upper and lower sections. The upper cable routing is schematically illustrated in  FIG. 1B  and the lower cable routing is schematically illustrated in  FIG. 1C , in which the cable fixture points are circled. The pulley systems  104 ,  105  accommodate the dual cable configuration. 
     Turning to  FIG. 2 , an enlarged view of platform  101  and robot arms  201  is depicted. The end-effector, dual cable robot gondola-based working platform  101  includes robot arm(s)  201  with tools  207 ,  208 , power and consumable supply system  202 , cable routing system  203  and  204 . The platform  101  may optionally include a bumper and roller that avoid the platform from accidentally colliding to with building surface. 
     The robot arm  201  may be selected from any type of programmable mechanical arm that typically includes various links coupled together with joints that permit rotational or translational movement. At the distal end of the robot is an end effector for holding and manipulating a tool. The robot arm is selected based on a desired number of degrees of freedom. A degree of freedom is a mode of motion for the robot arm. The total number of degrees of freedom define the ability of the robot arm to access any location at an arbitrary angle within a three-dimensional volume. For example, the human arm has at least six degrees of freedom, meaning that it can move forward and backward, up and down, left and right including changes in orientation and rotation in a 3D volume. Typically, the robot arm(s) of the present invention are selected to have at least 6 degrees of freedom such that it can replicate the motion of the human arm. Additional degrees of freedom permit the robot to perform the same task from different positions and may be selected depending upon the types of building maintenance to be performed. 
     Robot arm  201  is responsible for the complicated human-like motion which is required for a building maintenance task. For example, for cleaning applications, one robot arm may carry a window wiper  503  (see  FIG. 5A ) and another arm may carry a sponge for moistening the window surface and absorbing extra water droplets during the wiping motion. Also, for façade painting applications, the robot arm  201  performs paint application using a paint roller tool and liquid paint feeding system. 
     An optional power and consumable supply system  202  supplies the power to drive the robot arm(s) and all on-board electrical components (e.g., optional sensors and cameras). It may include a reservoir for holding water and detergent for façade cleaning and paint for façade painting. Inspection tools or work tools can also be mounted, including tool changer carousels, and obtain electricity from the supply system  202 . Alternatively, the power and consumable supply system may be located remotely, either on the ground or the roof, with electrical cables and liquid supply cables extending to the robot arms from the remote supply system. 
     In order to accommodate the four pairs of cables, pulley system  203  and  204  is provided. Pulleys  204  are used for the platform  101  rolling and moving from all 4 cables. Roller  203  is used to guide the cable from entering the pulleys  204  when the platform is at different positions. 
     Turning to  FIG. 3A , a winch and pulley system  300  is depicted. System  300  can route both upper and lower pairs of cables. System  300  positions the end-effector platform  101  at a distance from the building façade by adjusting the cable suspension system and the location of the fixed end. The actual adaptation of dual cable robot system depends on actual building design and working environment, where the winch systems may vary, as well as different locations of the driving motor. To assist in maintaining the position of platform  101  an optional spacer arm(s) may be positioned extending between the platform to the building façade. The spacer arm(s) may be equipped with sensor to assist in mapping the building façade and optional cameras so that a human operator may inspect the building façade and the work performed by the robot arms  201 . A spacer arm may also be positioned extending from a side of the platform  101  in order to sense approaching projections from the building façade. 
     The cable routing suspension system  104  in  FIG. 3A  can be divided into a cable pulley system and a suspension system. In the embodiment of  FIG. 3A , a single suspension system can route two cables to travel. A cable  122  ( FIG. 1 ) attached to the top corner of platform  101  will pass through the left channel of pulley  301 , then route to pulley  302 , followed by pulley  303 . From pulley  303 , the cable  122  will pass through the upper pulley of platform pulley  204  ( FIG. 2 ) and travel back to cable fixture  306 . The side view of the upper cable routing is shown in  FIG. 1B . The cable  124 , attached at the lower corner of platform  101 , will pass through the right channel of pulley  301 , to pulley  304 , through pulley  305 . From pulley  305 , the cable  124  travels to pulley  308  ( FIG. 3B ) which may be mounted on the ground or on the base of the building, through the lower pulley of platform pulley  204  to the cable fixture  309  ( FIG. 3B ). The side view of the lower cable routing is shown in  FIG. 1C . Note that additional cables can be routed by system  104  when additional pulleys are provided. Because the cable routing suspension system  104  is able to adapt to different building façade configurations with various arbitrary protruding elements, the length of the suspension system  311  arm can be adjusted by screws at  307 . 
     As shown in  FIG. 1 , the actuating units  102  are installed at the roof level of the targeted building; however, at the ground level, there is only passive pulley system as seen in  FIG. 3B , which contains a pulley  308  for translating the cable from roof to the platform  101 , and a cable fixture point for lower cable. Alternatively, the system may be configured such that the actuating units  102  are provided at the ground level, for example, if the actuators are portable units that are brought to the building site for the period of building maintenance. 
     Turning to  FIG. 4 , the cable winch and actuator unit  102  is responsible for controlling the cable pairs, moving end-effector platform  101  to any desired position along the building facade.  FIG. 4  shows a compact design of the unit, where two sets of actuators are situated together to drive both cable pairs  122  and  124 . Winch  401  is used to accumulate cable, and it is driven by a motor  404  using the belt system  402 . The belt is also connected to a cable outlet  403 , which will travel along the linear rail  405  and guide the cable to towards cable winch  401 in a controlled manner. Motor  404  receives a drive signal from controller  103  and drives the winch for controlling the cable length as a result, thus controlling the motion of platform  101 . 
     As building façades will have a large variety of different architectural features (protruding elements, curved surfaces, air conditioners or other mechanical systems), the non-flat façade makes the cleaning or painting motion much difficult and difficult for automation. In the system of the present invention, the suspension mechanism causes the platform  101  to be maintained at a sufficient distance from the building façade to avoid various protruding elements. Consequently, robot arm(s)  201  is configured to reach the surface to be cleaned or painted according to the shape of the façade while the platform  101  is driven. In addition to the length of the robot arm itself the robot arm may extend to reach of the tool through extension rods in order to expand the reach an additional meter or more. 
     Turning to  FIG. 5A , a close-up of robot arm  201  is depicted, along with a tool for window cleaning. The robot arm includes six degrees of freedom; however, other numbers of degrees of freedom may also be used. A wiper system  502  is mounted at the distal end of robot arm  201 . The wiper system  502  is specially designed for the dual cable robot system; as shown in  FIG. 5B , it includes at least three major components: the cleaning blade  503 , a wiper-robot arm adaptor  504 , and cleaning fluid dispensing system  505 . The cleaning blade  503  may include rubber scraping element which scrapes applied cleaning fluid from a window. An optional force sensor may be included to dynamically maintain the appropriate level of force on the surface to be cleaned regardless of the irregularity of that surface. The force sensor can be positioned within adapter  504  or elsewhere within the robot arm. The force sensor provides at least one degree of freedom of force sensing capability that detects the force experienced by the blade  503 . The cleaning fluid dispensing system  505  is mounted at the adaptor and positioned to distribute cleaning fluid onto the cleaning surface adjacent to the rubber blade  503 . The cleaning fluid dispensing system  505  is fed by a pump associated with platform reservoir  202  or, alternatively, fed by a pump associated with rooftop unit  103 . 
     When cleaning fluid is applied to a window surface, the fluid may splash and quickly flow downward, away from the target region. A robot arm equipped with a sponge may be used to collect excess cleaning solution as the robot arm with the wiper performs the cleaning task. Both arms may collaborate in the cleaning activity, maximizing the cleaning effect and avoiding streaks from dripping cleaning fluid.  FIG. 6  illustrates a robot arm equipped with a sponge roller for cooperating with the robot arm of  FIGS. 5A-5B . In  FIG. 6A , a sponge roller  601  is mounted at the distal end a second robot arm  201 . The cleaning fluid-absorbing sponge  601  is specially designed for the dual cable robot system, as shown in  FIG. 6B , it includes two major portions: the cleaning fluid-absorbing roller  602  and the sponge-robot arm adaptor  603 . The robot arm  201  drives the roller  602  to absorb excess cleaning fluid in cooperation with the wiper blade-holding robot arm. As with the wiper blade-holding robot, a force sensor may be included in the adapter  603  or elsewhere on the robot arm itself. The force sensor provides at least one degree of freedom which detects the force experienced by the sponge  602  when in contact with building façade. When desiring to maintain a set level of force, the robot arms will adjust their length and pressure when there is a protrusion or building curvature in the path of the cleaning tool. 
     Façade painting can be carried out with the paint roller system  701  as shown in  FIG. 7A . The painting system is specifically designed for the dual cable robot system of the present invention. The roller used can be refilled continuously using a special type of roller and paint pumping system. A paint roller  701  system is mounted on the distal end of robot arm  201 . As seen in  FIG. 7B , it includes 3 major components: a continuous paint roller  702 , a roller/robot arm adaptor  703  and paint-feeding system  704 . The robot arm  201  drives the paint roller  702  to apply paint over the façade surface. A force sensor can be included in adapter  703  or within the robot arm  201 . The force sensor provides a at least one degree of freedom which detects the force experienced by the roller  702  when in contact with building façade. Paint can be supplied into the paint roller from input system  704  by a pump associated with platform reservoir  202  or, alternatively, from a reservoir in unit  103  positioned on the roof. 
     It should be understood that the examples and embodiments described herein are for illustrative purposes only and that various modifications or changes in light thereof will be suggested to persons skilled in the art and are to be included within the spirit and purview of this application and the scope of the appended claims. In addition, any elements or limitations of any invention or embodiment thereof disclosed herein can be combined with any and/or all other elements or limitations (individually or in any combination) or any other invention or embodiment thereof disclosed herein, and all such combinations are contemplated with the scope of the invention without limitation thereto.