Resource-constrained environment-oriented obstacle avoidance system and method

Abstract

The invention relates to the technical field of navigation obstacle avoidance, and discloses a resource-constrained environment-oriented obstacle avoidance system with high reliability, which comprises an attitude sensing module (140) for acquiring attitude parameters of a controlled object in three-dimensional space attitude parameter operation in real time, an obstacle avoidance sensing module (200), a main control module (110) and an execution module (150), the main control module (110) is used for receiving the attitude parameter and the dynamic distance signal, and correspondingly outputting an adjustment signal according to the current attitude parameter and the dynamic distance signal; and the execution module (150) controls the motion posture of the controlled object according to the adjustment signal, so that the controlled object avoids the front obstacle in real time.

Description

Technical Field

[0001] The present invention relates to the technical field of navigation and obstacle avoidance, and more particularly to an obstacle avoidance system and method for resource-constrained environments. Background Art

[0002] Research or develop navigation and obstacle avoidance products for devices with limited computing power, storage, and energy (such as drones, robots, or IoT devices). These navigation and obstacle avoidance systems typically involve sensors collecting and providing real-time feedback on data during travel. However, due to the limited sensing range of these sensors, they cannot meet the requirements for sensing non-line-of-sight environments, such as ultra-long distances and obstructed areas. Furthermore, they cannot provide timely information and feedback on emergencies occurring along the route. Summary of the Invention

[0003] The technical problem to be solved by the present invention is that the above-mentioned sensors in the existing technology have limited perception distance and cannot meet the requirements of non-line-of-sight environment perception such as ultra-long distance and obstructed areas, and cannot obtain and feedback information of emergencies occurring on the line in a timely manner. The present invention provides a highly reliable obstacle avoidance system and method for resource-constrained environments.

[0004] The technical solution adopted by the present invention to solve the technical problem is to construct an obstacle avoidance system for resource-constrained environments, which has:

[0005] A posture sensing module is used to obtain the posture parameters of the controlled object in three-dimensional space in real time;

[0006] an obstacle avoidance sensor module, which is used to detect a dynamic distance signal between the controlled object and an obstacle in front;

[0007] a main control module, configured to receive the posture parameters and the dynamic distance signal fed back by the posture sensing module and the obstacle avoidance sensing module, and output an adjustment signal corresponding to the current posture parameters and the dynamic distance signal;

[0008] The execution module is used to receive the adjustment signal and control the motion posture of the controlled object according to the adjustment signal, so that the controlled object can avoid the obstacle in front in real time.

[0009] In some embodiments, the posture sensing module includes at least one posture sensor for obtaining rotation, tilt and / or rotational posture parameters of the controlled object in three dimensions, and converting the rotation, tilt and / or rotational posture parameters into electrical signals or digital data;

[0010] The signal output terminal of the posture sensor is connected to a signal input terminal of the main control module for receiving the rotation, tilt and / or rotation posture parameters.

[0011] In some embodiments, the obstacle avoidance sensing module includes at least an infrared obstacle avoidance sensor, which is used to detect a dynamic distance signal between the controlled object and the obstacle in front.

[0012] The signal output end of the infrared obstacle avoidance sensor is connected to another signal input end of the main control module for receiving the dynamic distance signal.

[0013] In some embodiments, the infrared obstacle avoidance sensor has a detection distance of 100 cm to 350 cm and a detection angle of -25° to 65°.

[0014] In some embodiments, the obstacle avoidance sensor module further includes an operational amplifier.

[0015] The inverting terminal of the operational amplifier is used to receive the dynamic distance signal.

[0016] The non-inverting terminal of the operational amplifier is connected to the common terminal,

[0017] The output end of the operational amplifier is connected to the signal input end of the infrared obstacle avoidance sensor.

[0018] In some embodiments, the execution module includes at least a first control branch, a second control branch, a third control branch, and a fourth control branch.

[0019] The signal input ends of the first control branch, the second control branch, the third control branch and the fourth control branch are respectively connected to the signal output end of the main control module, and are used to receive the adjustment signal and control the motion posture of the controlled object according to the input adjustment signal.

[0020] In some embodiments, the first control branch includes at least a first MOS transistor.

[0021] The second control branch at least includes a second MOS transistor,

[0022] The third control branch at least includes a third MOS transistor,

[0023] The fourth control branch at least includes a fourth MOS transistor, wherein:

[0024] The gate of the first MOS tube is connected to the first signal output terminal of the main control module through a sixth resistor.

[0025] The drain of the first MOS tube is connected to the first control terminal,

[0026] The source of the first MOS tube is connected to the common terminal,

[0027] The gate of the second MOS tube is connected to the second signal output terminal of the main control module through a seventh resistor.

[0028] The drain of the second MOS tube is connected to the second control terminal.

[0029] The source of the second MOS tube is connected to the common terminal,

[0030] The gate of the third MOS tube is connected to the third signal output terminal of the main control module through the eighth resistor.

[0031] The drain of the third MOS tube is connected to the third control terminal.

[0032] The source of the third MOS tube is connected to the common terminal,

[0033] The gate of the fourth MOS tube is connected to the fourth signal output terminal of the main control module through a ninth resistor.

[0034] The drain of the fourth MOS tube is connected to the fourth control terminal,

[0035] The source of the fourth MOS tube is connected to the common end.

[0036] In some implementations, the first MOS transistor, the second MOS transistor, the third MOS transistor, and the fourth MOS transistor are selected to be N-channel enhancement-mode MOS transistors.

[0037] In a second aspect, an obstacle avoidance method for a resource-constrained environment is applied to the above-mentioned obstacle avoidance system for a resource-constrained environment, and includes the following steps:

[0038] S101, used for obtaining the posture parameters of the controlled object in three-dimensional space posture parameter operation in real time;

[0039] S102, detecting a dynamic distance signal between the controlled object and a front obstacle;

[0040] S103, receiving the posture parameters and the dynamic distance signal fed back by the posture sensing module and the obstacle avoidance sensing module, and outputting an adjustment signal according to the current posture parameters and the dynamic distance signal;

[0041] S104 , receiving the adjustment signal, and controlling the motion posture of the controlled object according to the adjustment signal, so that the controlled object avoids the obstacle in front in real time.

[0042] The obstacle avoidance system for resource-constrained environments described in the present invention includes a posture sensing module for real-time acquisition of posture parameters of a controlled object in three-dimensional space, an obstacle avoidance sensing module, a main control module, and an execution module. The main control module receives posture parameters and dynamic distance signals and outputs adjustment signals corresponding to the current posture parameters and dynamic distance signals. The execution module controls the motion posture of the controlled object based on the adjustment signals, enabling the controlled object to avoid obstacles ahead in real time. Compared with the prior art, the posture sensing module and the obstacle avoidance sensing module feed back the real-time detected posture and fault signals to the main control module. The main control module outputs adjustment signals to control the execution module based on the feedback signals, thereby controlling the controlled object to make timely dynamic adjustments. This effectively addresses the problem that the sensor's limited sensing range cannot meet the requirements for sensing non-line-of-sight environments such as ultra-long distances and obstructed areas, and that it cannot timely acquire and feedback information about emergencies occurring on the line. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] The present invention will be further described below with reference to the accompanying drawings and embodiments, in which:

[0044] Figure 1 This is a schematic circuit diagram of a main control module of an embodiment of an obstacle avoidance system for resource-constrained environments provided by the present invention;

[0045] Figure 2 This is a schematic circuit diagram of a posture sensing module according to an embodiment of an obstacle avoidance system for resource-constrained environments provided by the present invention;

[0046] Figure 3 This is a schematic circuit diagram of an execution module of an embodiment of an obstacle avoidance system for resource-constrained environments provided by the present invention;

[0047] Figure 4 This is a circuit schematic diagram of an obstacle avoidance sensor module according to an embodiment of an obstacle avoidance system for resource-constrained environments provided by the present invention. DETAILED DESCRIPTION

[0048] In order to have a clearer understanding of the technical features, purposes and effects of the present invention, specific embodiments of the present invention are now described in detail with reference to the accompanying drawings.

[0049] like Figure 1-Figure 4 As shown, in the first embodiment of the obstacle avoidance system for resource-constrained environments of the present invention, the obstacle avoidance system for resource-constrained environments includes a main control module 110, a posture sensing module 140, an execution module 150 and an obstacle avoidance sensing module 200.

[0050] The main control module 110 has the functions of logic operation, data / signal processing, signal identification / analysis and control / adjustment of signal output;

[0051] The posture sensing module 140 is used to obtain changes in the posture parameters of the controlled object in three-dimensional space, including information such as position, direction and angle;

[0052] The obstacle avoidance sensor module 200 is used to detect the dynamic distance signals between the controlled object and obstacles in front, above, or to the left and right of the controlled object during its movement. Specifically, the obstacle avoidance sensor module 200 can output an infrared beam at a certain angle. When the light encounters an object, it will be reflected back. After detecting the reflected light, the dynamic distance signal between the obstacle and the controlled object can be calculated through the geometric triangulation relationship of the structure.

[0053] The execution module 150 is used to receive the adjustment signal output by the main control module 110 and control the motion posture of the controlled object in three-dimensional space according to the adjustment signal to make an operation posture to avoid obstacles in time;

[0054] Specifically, the posture sensing module 140 is used to obtain the posture parameters / information of the controlled object in the three-dimensional space posture parameter operation in real time, and output the obtained posture parameters / information to the main control module 110;

[0055] Furthermore, the obstacle avoidance sensor module 200 is used to detect the dynamic distance signal between the controlled object and the obstacle in front during operation, and output the acquired dynamic distance signal to the main control module 110;

[0056] The signal input end of the main control module 110 is connected to the signal output end of the posture sensing module 140 and the obstacle avoidance sensing module 200, respectively, for receiving the posture parameters and dynamic distance signals fed back by the posture sensing module 140 and the obstacle avoidance sensing module 200, and performing analysis and processing based on the current posture parameters and dynamic distance signals, and outputting corresponding adjustment signals after analysis and processing;

[0057] Furthermore, the signal input end of the execution module 150 is connected to the signal output end of the main control module 110, and is used to receive the adjustment signal output by the main control module 110, and control the motion posture of the controlled object according to the input adjustment signal, so as to control the controlled object to avoid obstacles in front in real time.

[0058] By using this technical solution, the real-time detected posture and fault signals are fed back to the main control module 110 through the posture sensing module 140 and the obstacle avoidance sensing module 200. The main control module 110 outputs an adjustment signal to the control execution module 150 according to the feedback signal, thereby controlling the controlled object to make dynamic adjustments in a timely manner. This can effectively solve the problem that the sensor's perception distance is limited and cannot meet the perception requirements of non-line-of-sight environments such as ultra-long distances and obstructed areas, and it is also impossible to obtain and feedback information on emergencies occurring on the line in a timely manner.

[0059] In some embodiments, as Figure 2As shown, in order to obtain the posture parameters of the controlled object in three-dimensional space, a posture sensor U104 can be set in the posture sensing module 140, which is used to obtain information such as the position, direction and angle of the controlled object in three dimensions;

[0060] Specifically, the attitude sensor U104 is used to obtain the rotation, tilt and / or rotation attitude parameters of the controlled object in three dimensions, and convert the rotation, tilt and / or rotation attitude parameters into electrical signals or digital data;

[0061] The signal output end of the posture sensor U104 (corresponding to pins 23 and 24) is connected to a signal input end of the main control module 110 (corresponding to pins 27 and 28). The main control module 110 is used to receive rotation, tilt and / or rotation posture parameters, analyze and process the input posture parameters, and then output corresponding adjustment signals.

[0062] In some embodiments, as Figure 4 As shown, in order to accurately obtain the dynamic distance signal between the controlled object and the obstacle in front, an infrared obstacle avoidance sensor U201 can be set in the obstacle avoidance sensor module 200, which is used to detect the dynamic distance signal between the controlled object and the obstacle in front. The detection distance is 100cm~350cm and the detection angle is -25°~65°;

[0063] Specifically, the signal output end (corresponding to pin 4) of the infrared obstacle avoidance sensor U201 is connected to another signal input end (corresponding to pin 19) of the main control module 110, which is used to receive the dynamic distance signal, analyze and process the input dynamic distance signal, and then output the corresponding adjustment signal.

[0064] In some embodiments, as Figure 4 As shown, in order to improve the accuracy of the output dynamic distance signal, an operational amplifier A201 can be set in the obstacle avoidance sensor module 200, which has the function of signal amplification;

[0065] Specifically, the inverting terminal (corresponding to pin 3) of the operational amplifier A201 is connected to one end of the infrared receiver LED4 through the eleventh capacitor C202 and the fifteenth resistor R203 connected in series, and is used to receive the dynamic distance signal or light wave signal fed back by the infrared transmitter LED3.

[0066] The non-inverting terminal of operational amplifier A201 (corresponding to pin 2) is connected to the common terminal.

[0067] The output end of the operational amplifier A201 (corresponding to pin 6) is connected to the signal input end (corresponding to pin 7) of the infrared obstacle avoidance sensor U201 through the twelfth capacitor C203, and the amplified dynamic distance signal is input into the infrared obstacle avoidance sensor U201. The infrared obstacle avoidance sensor U201 performs operation processing (such as angle / distance) on the input dynamic distance signal, and then outputs it to the main control module 110, which analyzes and processes the input dynamic distance signal and then outputs an adjustment signal accordingly.

[0068] In some embodiments, as Figure 3 As shown, in order to ensure the stability of the operation of the controlled object, a first control branch 151, a second control branch 152, a third control branch 153 and a fourth control branch 154 can be set in the execution module 150, wherein the above control branches are respectively used to control the propellers;

[0069] Specifically, the signal input terminal (corresponding to D3) of the first control branch 151 is connected to the signal output terminal (corresponding to pin 1) of the main control module 110, and is used to receive the first adjustment signal and control the motion posture of the controlled object according to the input first adjustment signal;

[0070] The signal input terminal (corresponding to D9) of the second control branch 152 is connected to the signal output terminal (corresponding to pin 13) of the main control module 110, and is used to receive the second adjustment signal and control the motion posture of the controlled object according to the input second adjustment signal;

[0071] The signal input terminal (corresponding to D11) of the third control branch 153 is connected to the signal output terminal (corresponding to pin 15) of the main control module 110, and is used to receive the third adjustment signal and control the motion posture of the controlled object according to the input third adjustment signal;

[0072] The signal input end (corresponding to D10) of the fourth control branch 154 is connected to the signal output end (corresponding to pin 14) of the main control module 110, and is used to receive the fourth adjustment signal and control the motion posture of the controlled object according to the input fourth adjustment signal.

[0073] In some embodiments, as Figure 3 As shown, in order to ensure the stability of the operation of the controlled object, the first control branch 151 may include at least a first MOS transistor Q1, and

[0074] The second control branch 152 at least includes a second MOS transistor Q2, and

[0075] The third control branch 153 at least includes a third MOS transistor Q3, and

[0076] The fourth control branch 154 includes at least a fourth MOS transistor Q4, wherein the MOS transistor is selected as an N-channel enhancement type MOS transistor and has a switch function;

[0077] Specifically, the gate of the first MOS transistor Q1 is connected to the first signal output terminal (corresponding to pin 1) of the main control module 110 through the sixth resistor R106, and is used to receive the first adjustment signal, and control the working state of the first MOS transistor Q1 by adjusting the duty cycle of the first adjustment signal, thereby controlling the speed of the corresponding propeller;

[0078] The drain of the first MOS transistor Q1 is connected to the first control terminal (corresponding to S1-2).

[0079] The source of the first MOS tube Q1 is connected to the common terminal.

[0080] The gate of the second MOS transistor Q2 is connected to the second signal output terminal (corresponding to pin 13) of the main control module 110 via the seventh resistor R107, and is used to receive the second adjustment signal and control the working state of the second MOS transistor Q2 by adjusting the duty cycle of the second adjustment signal, thereby controlling the speed of the corresponding propeller;

[0081] The drain of the second MOS transistor Q2 is connected to the second control terminal (corresponding to S2-2).

[0082] The source of the second MOS tube Q2 is connected to the common terminal.

[0083] The gate of the third MOS transistor Q3 is connected to the third signal output terminal (corresponding to pin 15) of the main control module 110 via the eighth resistor R108, and is used to receive the third adjustment signal and control the working state of the third MOS transistor Q3 by adjusting the duty cycle of the third adjustment signal, thereby controlling the speed of the corresponding propeller;

[0084] The drain of the third MOS tube Q3 is connected to the third control terminal (corresponding to S3-2).

[0085] The source of the third MOS tube Q3 is connected to the common terminal.

[0086] The gate of the fourth MOS transistor Q4 is connected to the fourth signal output terminal (corresponding to pin 14) of the main control module 110 through the ninth resistor R109, and is used to receive the fourth adjustment signal and control the operating state of the fourth MOS transistor Q4 by adjusting the duty cycle of the fourth adjustment signal, thereby controlling the speed of the corresponding propeller;

[0087] The drain of the fourth MOS transistor Q4 is connected to the fourth control terminal (corresponding to S4-2).

[0088] The source of the fourth MOS transistor Q4 is connected to the common terminal.

[0089] In a second aspect, an obstacle avoidance method for a resource-constrained environment is applied to the above-mentioned obstacle avoidance system for a resource-constrained environment, and includes the following steps:

[0090] S101, for obtaining the posture parameters of the controlled object in three-dimensional space posture parameter operation in real time, and feeding back the posture parameters to the main control module 110;

[0091] S102, detecting a dynamic distance signal between the controlled object and the obstacle ahead, and feeding the dynamic distance signal back to the main control module 110;

[0092] S103, the main control module 110 is used to receive the posture parameters and dynamic distance signals fed back by the posture sensing module 140 and the obstacle avoidance sensing module 200, and output an adjustment signal according to the current posture parameters and dynamic distance signals;

[0093] S104 , the execution module 150 is configured to receive the adjustment signal and control the motion posture of the controlled object according to the adjustment signal, so that the controlled object can avoid obstacles in front in real time.

[0094] Specifically, when the infrared obstacle avoidance sensor U201 detects an obstacle signal in front, the output end of the infrared obstacle avoidance sensor U201 continuously outputs a low-level signal. The detection distance of this module is 100cm~350cm, and the detection angle is -25°~65°;

[0095] Among them, the starting frequency of the infrared obstacle avoidance sensor U201 is 38KHz; the infrared carrier signal comes from pin 1, that is, the carrier signal is consistent with the capture center frequency, which can greatly improve the anti-interference characteristics;

[0096] Pins 5 and 6 of the infrared obstacle avoidance sensor U201 are usually grounded through the fourteenth capacitor C205 and the fifteenth capacitor C206, respectively, to form an output filter network and a loop single-stage low-pass filter network;

[0097] The capacitor connected to pin 5 of the infrared obstacle avoidance sensor U201 determines the capture bandwidth of the phase-locked loop. The larger the capacitance, the narrower the loop bandwidth. The capacitance of the capacitor connected to pin 5 should be at least twice that of the capacitor connected to pin 6.

[0098] Among them, the 4th pin of the infrared obstacle avoidance sensor U201 outputs a 38KHz frequency, and the 7th pin inputs the signal received by the infrared receiver LED4, which can prevent the difference in the receiving and transmitting frequencies caused by changes in the surrounding environment and component parameters, and realize the synchronous automatic tracking of the infrared emission and receiving working frequencies, which greatly enhances the stability and anti-interference ability of the circuit;

[0099] In addition, the 38KHz center frequency output from pin 1 of the infrared obstacle avoidance sensor U201 is output to the first transistor Q201, amplified by the first transistor Q201, and the signal is output to the infrared transmitter LED3. The adjustable resistor RT1 can change its transmission power. The signal is received by the infrared receiver LED4, amplified by the operational amplifier A201, and output to the input pin 7 of the infrared obstacle avoidance sensor U201. The output of its pin 1 changes from the default high level to a low level, and the infrared transmitter LED3 has a voltage difference. The infrared receiver LED4 continuously receives the obstacle signal ahead fed back by the infrared transmitter LED3. At the same time, the signal from pin 4 is output to the main control module 110, and the main control module 110 controls the operation of the execution module 150 according to the change in level to achieve obstacle avoidance.

[0100] The embodiments of the present invention are described above in conjunction with the accompanying drawings, but the present invention is not limited to the above-mentioned specific implementation methods. The above-mentioned specific implementation methods are merely illustrative and not restrictive. Under the guidance of the present invention, ordinary technicians in this field can also make many forms without departing from the scope of protection of the present invention and the claims, all of which are protected by the present invention.

Claims

1. An obstacle avoidance system for resource-constrained environments, characterized in that: have: A posture sensing module is used to obtain the posture parameters of the controlled object in three-dimensional space in real time; an obstacle avoidance sensor module, which is used to detect a dynamic distance signal between the controlled object and an obstacle in front; a main control module, configured to receive the posture parameters and the dynamic distance signal fed back by the posture sensing module and the obstacle avoidance sensing module, and output an adjustment signal corresponding to the current posture parameters and the dynamic distance signal; The execution module is used to receive the adjustment signal and control the motion posture of the controlled object according to the adjustment signal, so that the controlled object can avoid the obstacle in front in real time.

2. The obstacle avoidance system for resource-constrained environments according to claim 1, characterized in that: The attitude sensing module includes at least one attitude sensor, which is used to obtain the rotation, tilt and / or rotation attitude parameters of the controlled object in three dimensions and convert the rotation, tilt and / or rotation attitude parameters into electrical signals or digital data; The signal output terminal of the posture sensor is connected to a signal input terminal of the main control module for receiving the rotation, tilt and / or rotation posture parameters.

3. The obstacle avoidance system for resource-constrained environments according to claim 1, characterized in that: The obstacle avoidance sensing module includes at least an infrared obstacle avoidance sensor, which is used to detect the dynamic distance signal between the controlled object and the obstacle in front. The signal output end of the infrared obstacle avoidance sensor is connected to another signal input end of the main control module for receiving the dynamic distance signal.

4. The obstacle avoidance system for resource-constrained environments according to claim 3, characterized in that: The infrared obstacle avoidance sensor has a detection distance of 100 cm to 350 cm and a detection angle of -25° to 65°.

5. The obstacle avoidance system for resource-constrained environments according to claim 3 or 4, characterized in that: The obstacle avoidance sensor module also includes an operational amplifier, The inverting terminal of the operational amplifier is used to receive the dynamic distance signal. The non-inverting terminal of the operational amplifier is connected to the common terminal, The output end of the operational amplifier is connected to the signal input end of the infrared obstacle avoidance sensor.

6. The obstacle avoidance system for resource-constrained environments according to claim 1, characterized in that: The execution module at least includes a first control branch, a second control branch, a third control branch and a fourth control branch. The signal input ends of the first control branch, the second control branch, the third control branch and the fourth control branch are respectively connected to the signal output end of the main control module, and are used to receive the adjustment signal and control the motion posture of the controlled object according to the input adjustment signal.

7. The obstacle avoidance system for resource-constrained environments according to claim 6, characterized in that: The first control branch at least includes a first MOS transistor, The second control branch at least includes a second MOS transistor, The third control branch at least includes a third MOS transistor, The fourth control branch at least includes a fourth MOS transistor, wherein: The gate of the first MOS tube is connected to the first signal output terminal of the main control module through a sixth resistor. The drain of the first MOS tube is connected to the first control terminal, The source of the first MOS tube is connected to the common terminal, The gate of the second MOS tube is connected to the second signal output terminal of the main control module through a seventh resistor. The drain of the second MOS tube is connected to the second control terminal. The source of the second MOS tube is connected to the common terminal, The gate of the third MOS tube is connected to the third signal output terminal of the main control module through the eighth resistor. The drain of the third MOS tube is connected to the third control terminal. The source of the third MOS tube is connected to the common terminal, The gate of the fourth MOS tube is connected to the fourth signal output terminal of the main control module through a ninth resistor. The drain of the fourth MOS tube is connected to the fourth control terminal, The source of the fourth MOS transistor is connected to the common terminal.

8. The obstacle avoidance system for resource-constrained environments according to claim 7, characterized in that: The first MOS transistor, the second MOS transistor, the third MOS transistor and the fourth MOS transistor are selected as N-channel enhancement mode MOS transistors.

9. An obstacle avoidance method for resource-constrained environments, characterized in that: The obstacle avoidance system for resource-constrained environments as described in any one of claims 1 to 8 comprises the following steps: S101, used for obtaining the posture parameters of the controlled object in three-dimensional space posture parameter operation in real time; S102, detecting a dynamic distance signal between the controlled object and a front obstacle; S103, receiving the posture parameters and the dynamic distance signal fed back by the posture sensing module and the obstacle avoidance sensing module, and outputting an adjustment signal according to the current posture parameters and the dynamic distance signal; S104 , receiving the adjustment signal, and controlling the motion posture of the controlled object according to the adjustment signal, so that the controlled object avoids the obstacle in front in real time.

Images