RU139571U1 - DEVICE FOR ORIENTATION AND NAVIGATION OF A MOBILE ROBOT TROLLEY WHEN MOVING IT ON A HORIZONTAL SURFACE IN A SPECIFIED ROOM - Google Patents

Abstract

A device for orienting and navigating a mobile robot carriage when moving along a horizontal surface in a given room in the absence of other dynamically moving objects, configured to install a mobile robot car with electric motors on a carriage, comprising distance sensors and an electronic memory unit for calculating and controlling sensors and carriage movement, characterized in that the device includes: four ultrasonic distance sensors located on the trolley of a mobile robot, taking into account the possible awn measure the distance to objects and walls in the room in four directions perpendicular to the direction of movement of the robot, namely: forward, backward, right and left; electronic unit for memory, calculation and control of ultrasonic distance sensors and trolley movement; outputs of ultrasonic distance sensors, configured to connect to the inputs of an electronic memory unit, calculate and control ultrasonic distance sensors and the movement of the trolley; outputs of the electronic block of memory, calculations and control of ultrasonic distance sensors and the movement of the trolley, made with the possibility of connecting the inputs of the triggering devices of ultrasonic distance sensors to measure the distance and devices of the block of electric motors of the trolley; In the memory of the electronic unit for memory, calculations and control of ultrasonic distance sensors and the movement of the trolley, a geometric map-plan of the premises is contained, containing the numbers of all rooms available for the robot, their geometric dimensions, namely the length and width, and the coordinates of the passages between the room

Description

The technical solution relates to robotics, namely, to navigation devices and determining the location of a mobile robot carriage in flat Cartesian coordinates when moving the robot carriage on a horizontal surface in a given room of a corridor-room type.

In modern robotics, one of the urgent tasks is the task of developing methods and devices for autonomous “intelligent” navigation of robots. With autonomous movement, the robot must be able to determine its location on the map with a given accuracy and to control its movement without human intervention. Therefore, the development of specialized “smart” devices and software tools for navigating mobile robots is relevant. According to the well-known definition given in the Wikipedia Internet encyclopedic resource, navigation is the process of managing some object that has its own methods of movement in a certain space of movement. In order to carry out such control, the robot must have an indication of the purpose of the movement, a certain algorithm for performing movements, a map of the area outlining possible ways of movement, and also a device capable of determining the orientation of the robot and its current location on the map. In the general case, this problem has not been completely solved today, and a single, universal method and device for orienting and navigating a mobile autonomous robot in any possible space of movements has not yet been created.

This technical solution is intended to solve one of the particular cases of this general problem - the case of moving a mobile robot in a room-type room (apartment, office, hospital wards, etc.) on the horizontal surface of one floor in the absence of dynamically moving other objects (people , mechanisms) in the field of view of the robot.

Today, there are many methods and devices for the autonomous orientation and navigation of mobile robots and robotic automated systems (autocars, cars, etc.) in space. It is widely known, for example, the method of orientation and navigation using satellite communication systems - Glonass, GPS, etc. (see Bobrovsky, S.N. Navigation of mobile robots // Journal. PC Week. - 2004. - No. 9. - C. 60-63). However, civilian organizations have access to GPS receivers capable of determining the location of an object only with an error of about 5 m, not more precisely, which is unacceptable in the conditions of domestic, hospital and / or office premises with comparable linear dimensions.

A device is known that combines a laser scanner and a GPS navigation system to clarify the coordinates of the position of an object in the GPS coordinate grid (application US 2006106533). The laser scanner works on the principle of a laser locator and from time to time updates the coordinates of the robot in the GPS grid. However, this device is very expensive in cost, heavy and complex in its construction and, in addition, it does not provide for determining the angle of rotation of the robot cart in the coordinate space, does not contain a map of the area, i.e. cannot link the location of the robot to the floor plan, and the GPS system often does not work indoors. Therefore, in general, this device is not applicable indoors.

It is also known a device based on the use of only one laser scanner-locator (US patent 4918607), operating on the principle of determining the distance from the delay of the backward reflected optical signal. The laser locator scanner is located on a rotating platform on the surface of the robot cart and scans the entire space around the robot during its movement, determining the distance to light-reflecting objects in the path of the robot. But this device is also very expensive in cost, does not contain a terrain map and has an additional significant drawback associated with the inability to obtain the required back-reflected light signal from black surfaces and mirror surfaces located at an angle to the axis of the scanning laser beam. Moreover, the laser beam and / or its reflection during the movement of the robot can get into the human eye, which is unacceptable from the point of view of safety. Therefore, this device is also not applicable in the conditions of domestic, hospital and / or office premises.

Safer methods and devices of location are also known - methods and devices based on the use of ultrasonic locators and passive vision systems (video cameras).

A device of a mobile robot is known (patent RU 274543), on a self-propelled cart of which a receiver and an ultrasonic signal transmitter are installed to detect an obstacle in the way of the movement of the robot. But this device only determines the presence of an obstacle along the line of movement of the robot and does not determine the location of the robot in the coordinates of the terrain map. The robot also does not have a terrain map for navigating its movement, therefore such a robot will simply move along the obstacle-free passages by the random walk method, as most well-known home vacuum cleaner robots do.

Also known are the Ultrasonic technological mobile robot (certificate for utility model RU 5541) and the mobile robot control system (patent for utility model RU 83858), which contain a set of ultrasonic sensors with receivers and emitters of ultrasound. However, these systems are very expensive because their proposed design and signal processing algorithm require the use of complex nodes to ensure the orientation of the robot - a cognitive graphics unit, a database unit and an arbitrary loop evaluation unit in the case of an Ultrasonic robot according to the certificate of RU 5541, as well as a neural network-classifier with a fuzzy logic unit and an electronic compass in the case of a mobile robot control system according to patent RU 83858.

Using a passive vision system, a method is known for adjusting the course of a mobile robot based on a device for determining the current location of the robot (patent RU 2210492), which contains an overview camera with a video card connected to a computer for recognizing basic characters on the ceiling. The invention allows to determine the location of the robot by the basic signs on the ceiling, i.e. determine its approximate location in a particular part of the room, as well as adjust the direction of its movement when an obstacle is detected. The disadvantage of this method and device is the necessary additional placement of special signs on the ceilings of the premises, which does not allow the robot to be used in an unprepared room. In addition, this method and device do not allow to calculate the Cartesian coordinates of the robot and its angle of rotation on the map of the area.

The closest in its operational characteristics to the claimed technical solution is a method for visually controlling the orientation of a mobile robot carriage when moving it on a horizontal surface in a given room, described in the description of patent for invention RU 2307730. This method is implemented as follows. Two different radiation sources (bulbs) are mounted on the trolley of a mobile robot at the same height. On the horizontal surface of the terrain where the robot is expected to move, a system of fixed reference points is created and a video camera is fixedly mounted. For each reference point on the image matrix of the video camera, an average point image of the radiation source is determined. From the images of the current positions of the radiation sources as the robot moves, first determine the images of the reference points that are not lying on one straight line, which then interpolate the positions of the radiation sources in a flat coordinate system, and also determine the angular position of the mobile robot carriage. This invention provides automatic accurate determination of the flat Cartesian coordinates and the angular position of the mobile robot carriage when moving along a horizontal surface in a given room.

The disadvantage of this method is that it is necessary to create special reference points in the room, and the video camera is not placed on the robot trolley, i.e. the use of the robot is possible only in one specially prepared room in the field of view of the video camera, or all rooms accessible for movement by the robot must be equipped with reference points and video cameras, which is expensive and requires the installation of additional communications (wires connecting the cameras to the computer, power cables for the cameras, etc.) P.).

In accordance with this, the task is set to eliminate all the above disadvantages. The authors propose an inexpensive, safe and mobile solution for the device of orientation and navigation of the mobile robot cart when it is moving in a given room on a horizontal surface, which could be located completely on the mobile robot cart that does not use hazardous laser radiation, does not require any additional premises fixed points, beacons, markings, signs, but functionally allows with a given accuracy sufficient for practical use, taking into account possible errors measurement methods of each sensor, determine the coordinates of the robot on the map of the area and its angular position in case of loss of orientation.

The proposed device is shown schematically in FIG. 1. The proposed device 1, placed on the trolley of a mobile robot 2 with electric motors 2a and 3b, contains 4 standard and inexpensive ultrasonic distance sensors 4a, 4b, 4c, 4g, for example, type HCSR04 (see Product User's Manual "Ultrasonic Sensor HCSR04" / Cytron Technologies Sdn. Bhd., Skudai, Malaysia, price in 2013 is about 5 USD per sensor) located on a mobile robot trolley (for short - a robot trolley) taking into account the possibility of measuring the distance to objects and walls in the room in 4 mutually perpendicular to the direction of movement of the robot - forward, backward, right, left. Also, the proposed device 1 contains an electronic unit for memory, calculation and control of ultrasonic distance sensors and the movement of the trolley (abbreviated as on-board computer) 5, which contains a geometric map of the premises and an algorithm for controlling the movement of the robot. The outputs of the ultrasonic distance sensors are made with the possibility of connecting to the inputs of the on-board computer 5a, and the outputs of the on-board computer 5b are made with the possibility of connecting the inputs of the control devices of ultrasonic sensors, namely, devices for triggering sensors for measurement, and devices of the block of electric motors of the cart, also controlled by commands from the on-board computer . The geometric map-plan of the premises is contained in the computer memory block and represents a list of objects — rooms and corridors of the premises — with the characteristic distinguishing features assigned to them: conditional numbers (names), geometric dimensions — the width (W) and length (L) of each room in meters, the number of the adjacent room with which the given room is connected by the entrance, as well as the left {X; Y} _L and right {X; Y} _R coordinates of the entrance to the room relative to the Cartesian axes X and Y, located on two adjacent to each other with room shadows - front (X) and left (Y), respectively.

The principle of forming a geometric map-plan of the premises and the adopted coordinate system for them are explained in FIG. 2 by the example of two rooms - a corridor and a room (any other number of rooms, their other configuration and geometry are easily generalized and implemented on the basis of this example by analogy). Each room - room 1 and corridor 2 - has its own coordinate system {X1; Y1} and {X2; Y2}, as well as its width and length {W ₁ , L ₁ } and {W ₂ , L ₂ }, respectively. The passage 3 from corridor 2 to room 1 is set by the coordinates {X1 _L Y1 = 0} _L , and {X1 _R ; Y1 = 0} _R in the coordinate system of room 1, which can easily be converted into the coordinate system of corridor 2, because . the width of the corridor W ₂ and the offset D _{1-2 of the} coordinates {X1 = 0} relative to {X2 = 0} are known. The room and the corridor may additionally contain furniture 4, the coordinates of which are not specified on the map. The robot truck containing the proposed device 5 at the initial time carries out its movement, for example, along the corridor 2 to the right with a speed V. In this case, in the RAM of the on-board computer of the proposed device, the number of the room in which it is located acts as the current location variable (number 2 in this case), and the length (L ₂ ) and width (W ₂ ) of this room are known to the device from the map of the premises. The proposed device during the movement of the trolley of the robot works and implements its functions as follows. In the case of a simple rectilinear movement of the robot carriage containing the proposed device (Fig. 3), the on-board computer constantly in a cycle issues a measurement start signal to each sensor and polls all its sensors, receiving information about the distance to the walls forward (r _f ), back (r _b ), to the right {r _r ) and to the left (r _l ). Since each measurement of r _i cannot be performed absolutely accurately and usually contains some measurement error (inaccuracy) Δr _{i, the} current coordinates of the robot cart in the coordinate system {X2; Y2} to reduce orientation errors are determined as the arithmetic mean of the results of 2 measurements:

,1st dimension:

,

where Δr _b and Δr _r are the possible (typical) errors of measuring the distances back (b) and to the right (r) (they are determined during testing of a robot carriage containing the proposed device);

2nd dimension:

,

,

where Δr _l and Δrf are the possible (typical) errors of measuring the distances forward (f) and to the left (l) (also determined by testing a robot carriage containing the proposed device);

and averaging:

.

.

In addition, in each measurement cycle, the ratios are controlled:

,

,

where ΔL ₂ and ΔW ₂ are the permissible errors in measuring the geometric dimensions of the premises (set by the robot developer). Checking conditions (5) and (6) constantly “confirms” the robot cart its location on the map - the fact of being in corridor 2 with geometric dimensions L ₂ and W ₂ taking into account possible measurement errors. The size of the robot itself in this algorithm is neglected. We believe that all distances are determined by sensors taking into account the known dimensions of the robot, i.e. all distances are measured from the center of mass of the robot.

Further, if the robot needs to go to room 1, then at one point in time of its movement, it will be in the position to the right of the passage (Fig. 4). The passage in the framework of the description of the principle of operation of this technical solution is always assumed to be free, i.e. the door is missing. At this point in time, the readings of the lateral ultrasonic distance sensors of the proposed device in total cease to satisfy condition (6). This will happen even if a small obstruction 4d appears on the right side of the device on the blind wall, changing the readings r _r , as shown in FIG. 4. Anyway, the sum of the distances r _r and r _l will be much larger than the width of the corridor W ₂ ± ΔW ₂ . This will mean that according to the location map to the left of the robot carriage, a passage to room 1 was detected. In this case, the proposed device remembers the current distance values r _r = r ₁ ∗ and r _l = r ₂ ∗, rotates the carriage with the robot 90 ° to the left so that the values r _b = r ₁ ∗ and r _f = r ₂ ∗ become true instead of them, and centers its position along the X axis in the center of the passage, based on the coordinates of the passage {X1 _L ; Y1 = 0} _L and { X1 _R ; Y1 = 0} _R in the coordinate system of room 1, as well as at the coordinate origin of the system {X1; Y1} known from the map with respect to the system {X2; Y2}. The coordinate X2 of the robot in this case will be determined by a simple relation:

After that, the carriage with the robot 5 enters the room 1 to a depth S (Fig. 5), the proposed device controls and determines the depth S according to the readings r _b and r _f similar to the algorithm according to formulas (1) - (4), namely:

S is defined as the arithmetic mean of two dimensions:

,1st dimension:

,

where (r _b ± Δr _b ) is the current measurement result of the distance back;

2nd dimension:

where (r _f + Δr _f ) is the current measurement result of the distance forward;

.and averaging:

.

The moment of crossing the line of passage 3 itself is determined by the robot carriage containing the proposed device 5, according to a sharp decrease, and then a sharp increase in the readings of the lateral ultrasonic distance sensors - at the time of crossing the passage they will show its width in total. At this point in time, the coordinate Y1 of the robot carriage in the coordinate system of room 1 is assumed to be zero (Y1 = 0 is assumed) and the readings r _b = r ₃ ∗ and r _f = r ₄ ∗ are stored.

The next step, the proposed device must determine the value of its coordinate Y1, because in this example, only from the offset S due to the presence of furniture 4a and 4d (see Fig. 5) it is impossible to directly calculate the coordinate Y1, and the value of the coordinate XI is already known from the condition that the trolley with robot 5 enters room 1 directly in the center of passage 3, t .e. from (7) it directly follows:

.

.

The proposed technical solution makes it easy to perform this operation. The YI coordinate of the trolley with the robot, which “entered” the room due to the displacement S, is defined again as the arithmetic mean of two measurements and calculations:

,1st dimension:

,

where (r _b ± Δr _b ) is the current measurement result of the distance back in position S;

,1st dimension:

,

where (r _f ± Δr _f ) is the current measurement result of the forward distance in position S;

.and averaging:

.

Further, the proposed device must check the size of room 1 according to the readings of ultrasonic distance sensors and compare them with the known values from the map by analogy with checking the ratios (5) and (6) to make sure that it is actually in the right room - in room 1. However, it may turn out that the back, front and / or side of the trolley with the robot, as shown in FIG. 5, there are also other pieces of furniture or other obstacles / objects that do not allow in this position the trolley with the robot to immediately measure the size of the room with a given accuracy. Then the trolley with the robot 5 begins to rotate around its axis, for example, to the right by an angle φ, as shown in FIG. 6 and FIG. 7, taking measurements and calculating the size of the room from simple geometric formulas. Comparing the calculated sizes with the dimensions known from the map depending on the angle of rotation of the robot, you can sooner or later, by scanning with several different angles φ, get the match with the dimensions from the map with a given accuracy if the cart with the robot is actually in the selected room with number 1 ( the sizes of rooms 1 and 2 do not match), or never get matches if the trolley with the robot is in another room - room 2. Here, when scanning along the angle φ, there can be several options for measuring distance It is shown, for example, in FIG 6 and FIG. 7 and, accordingly, several calculation options. However, all these options are obvious, their set is finite, therefore, all calculations for all options can easily be performed by the on-board computer of the proposed device, based on the school geometry course, i.e. the practical applicability of this algorithm is obvious. For example, for FIG. 6 the width of the room, defined as

,

,

where φ-θ = 90 °, will give the correct result within the allowable specified error ΔW ₁ . For FIG. 6. room length, defined as

will give the correct result within the allowable specified error ΔL ₁ .

If there is an obstacle in the path of any direction of measurement, the dimensions calculated using this direction will not coincide with the dimensions of the room indicated on the map. In this case, a decision is made on the room number according to calculations for other sizes, or the robot carriage is rotated to a different angle, performing new calculations at a new angle, until reliable matches are obtained, or until its rotation around the axis by 360 ° is complete. In the latter case, if it was not possible to obtain reliable matches in any measurements with a complete turn, a conclusion is made about the error of the current room number.

The same algorithm of simple geometric calculations allows the trolley of the robot 5, if it "lost" orientation, to completely re-determine its coordinates (x, y) and the angle of rotation (φ) in any room, knowing only the number of the room in which it is located, and its linear geometric dimensions (width W and length L) (Fig. 8). This is done according to the following algorithm.

Based on the readings of ultrasonic distance sensors, an error function E (x, y, θ) is compiled, determined for each room point and each angle of rotation of the robot φ, taking into account φ + θ = 90 °. The error function is the sum of the squares of the deviations of the readings of the sensors r _f , r _b , r _r , r _l from the true distances to the walls R _f , R _b , R _r , R _l in the measurement directions:

.

.

The true distances to the walls are determined from the general geometric relationships as follows:

,

,

where I _{[a, b]} (θ) is an indicator of the set [a, b] such that:

where Z is the set of all integers.

Next, one of the known numerical methods, for example, the gradient descent method (see Gill F., Murray W., Wright M. Practical optimization. Transl. From English. - M .: Mir, 1985.), is the minimum of the error function by ( 17) for some specific set of coordinates. These coordinates

and are the solution to the problem of determining the coordinates of the robot cart in any given room using the proposed device.

Thus, the proposed technical solution functionally allows, with a given accuracy, sufficient for practical use, to determine the coordinates of the robot cart on the map and its angular position when moving the robot cart on a horizontal surface in a given room of the corridor-room type.

Claims (1)

A device for orienting and navigating a mobile robot carriage when moving along a horizontal surface in a given room in the absence of other dynamically moving objects, configured to install a mobile robot car with electric motors on a carriage, comprising distance sensors and an electronic memory unit for calculating and controlling sensors and carriage movement, characterized in that the device includes: four ultrasonic distance sensors located on the trolley of a mobile robot, taking into account the possible awn measure the distance to objects and walls in the room in four directions perpendicular to the direction of movement of the robot, namely: forward, backward, right and left; electronic unit for memory, calculation and control of ultrasonic distance sensors and trolley movement; outputs of ultrasonic distance sensors, configured to connect to the inputs of the electronic memory unit, calculate and control ultrasonic distance sensors and the movement of the trolley; the outputs of the electronic memory unit, computing and controlling ultrasonic distance sensors and the movement of the trolley, configured to connect the inputs of the triggering devices of ultrasonic distance sensors to measure the distance and devices of the block of electric motors of the trolley; a geometric map-plan of the premises is contained in the memory of the electronic unit for memory, calculations and control of ultrasonic distance sensors and the movement of the cart; it contains the numbers of all rooms available for the robot, their geometric dimensions, namely length and width, and the coordinates of the aisles between the rooms, as well as the algorithm control the movement of the trolley of a mobile robot depending on the current coordinates of the robot and the purpose of its movement.

Images