自动清扫湖面漂浮物船外文文献翻译、中英文翻译、外文翻译

自动清扫湖面漂浮物船外文文献翻译、中英文翻译、外文翻译,自动,清扫,湖面,漂浮,外文,文献,翻译,中英文 附录一： 自动清扫湖面漂浮物船 摘要---在许多国家水面漂浮物的污染越来越严重，有人提议可以设计一艘自动清扫湖面漂浮物的船，这艘船是由太阳能电池供电。电池系统的过多充放电保护回路已被使用。超声波检测系统已被安装在船上并且能检测到船到湖边的距离。船的方向和位置是由在两次连续控制船的行驶方向使其在离岸边不远的环形区域内自动行驶的时间，船到岸边的距离确定。船上已经安装一个可以识别障碍物并自动避开检测到的障碍物的系统。在船的两侧安装螺旋桨来驱动船舶，可以使船舶灵活的改变方向。光敏电阻是用来确定它是在白天还是黑夜，船舶只有在夜晚环绕湖中一次就可以节省能量。无线遥控器是有用的，因为它可以使用船者更灵活方便的控制船。实验证明了设计的适用性。 关键词：自动的，漂浮物，超声波，清扫船，污染 I. 介绍 自然湖泊和所有的人工湖泊可以使人们的生活环境变得很美。现在人们的生活水平越来越高，很多人逢年过节或者在假期间，都会选择去一些景区游玩，但是有的人素质略显低，在公共场所乱丢垃圾。在一些河道以及湖泊的水面上我们可以看到许多漂浮物，这些漂浮物就会使水里的空气供应不足，从而导致水里的鱼最终也是漂浮在水面上，最终形成恶性循环。然而，随着人类活动的增加，湖面上漂浮物的污染越来越严重。对湖面上垃圾物的污染治理越来越迫切。[1] 由此可见湖泊里的水流速度很低，有时几乎为零，大部分漂浮物垃圾分布在湖边的一个区域。[2]目前，所有漂浮物垃圾经常是人工清理。[3]工作量大，花费时间久，成本贵，工作效率低。为了解决以上问题，我们已经设计了一艘自动清扫湖面漂浮物垃圾船。如图片1所示，一个模型船已经被研制出来了，已进行的实验证明了实验的适用性。 II. 清扫船的设计 清扫船主要由太阳能电池供电，这非常经济性，能够节约能源和保护环境。清扫船决定它自己的方向和位置可以以湖岸为参考系。清扫船主要是通过控制船在离湖边不远预设的区域内绕着湖边运转。同时，清扫船可以自动清扫垃圾。当超声波探测到前方有障碍物，清扫船就会自动变更方向。也设计了识别白天还是黑夜的电路。清扫船只有在夜晚环绕湖面一圈就可以节省能量了。通过实际环境确定在白天清扫漂浮物垃圾循环时间。遥控电路的设计，手动控制船舶的使用，这个在一些特殊的环境下极其有用，从而可以提高船舶的实用性。一种用于收集漂浮垃圾的机械设计，实现自动收集漂浮垃圾。 为了实现以上提到的功能，垃圾清扫船需要通过微处理器来控制。它需要能源供应系统，键盘和显示器，障碍物检测系统，船舶定位检测系统，运动控制系统，用于识别白天和夜晚的电路，远程控制系统，在图2中可以看出， 图2：清扫船的结构 A：单片机微处理系统设计 清扫船主要SCM系统是由一个SCM，晶体振荡器和一个监视时钟组成。SCM是AT89S52单片机，是爱特梅尔公司生产。它具有8K字节的芯片闪存，和256字节的RAM，两个16位定时器/计数器，两个外部中断，一个全双工UART。SCM的振荡频率是12MHZ，监视时钟在通电，断电等其它故障时会清零。监视时钟是MAX813，是MAXIM公司生产的，这家公司专门生产集成电路的功率检测和监视时钟定时器。 B：键盘和显示组件的设计 在清扫船中，ZLG7289已应用在键盘电路和显示组件电路，这两种电路是坐落在广州的一家公司生产的。一个ZLG7289芯片可以驱动7段LED管最高显示8为数字，条形图显示，或64个发光二极管和64键的键盘。它通过串行外接口[SPI]与单片机通信，并且只需要三个I/O引脚的单片机可以节约有限的资源。当按键被按时，ZLG7289的键栓就会变低。当读取低电平信号时，SCM可以通过SPI总线确定键盘的按键数量。将会有八个LED数码管显示和六个按键。系统可以获取LED数码管显示的距离值的距离检测。六个功能键主要用于设置的清扫船的控制参数。 C：运动控制系统设计 运动控制系统控制清扫船在湖泊里运动。从属系统可以探测到清扫船距离湖边的距离，并通过异步串行口发送到主控制系统上。通过两清扫船距离值主控制系统可以确定清扫船的位置和方向。在系统中超声波是用来测量距离的。超声波测距是利用反射式测距方法[5]，要测量的距离是根据在系统发出的超声波和系统接收到回波的时间计算的。每一个测距系统是是由一个独立的单片机控制发射超声波和接收超声波[6]。专用集成电路LM1812完成了超声波发送任务。当接收回波的任务由红外接收模块CX20106完成。当超声波的传输控制信号，单片机内部定时器被同时启动。集成电路CX20106在接收到回波时，外部中断器将会停止读取时间信号，此时会发送一个低电平信号，清扫船和物体之间的距离可以通过定时器的数据计算。清扫船上设有两个超声波测距系统，其中一个安装在船的前面，被记为A，另一个是放置在船的右侧，被标记为B。 这两个传感器每隔两秒就会测量一次船和湖边的距离，根据两个连续时间段内的距离可以确定清扫船的位置和方向。有几种不同的情况如下所述： 第一种情况是：通过A传感器第一次和第二次测量的距离超出了额定范围，也就是说超过3m以上，和用传感器B所测结果是一样的，约60厘米，此时此刻，清扫船被认为是和湖边是平行的。 第二种情况是：通过A传感器第一次和第二次测量的距离超出了额定范围，因此，说明前面没有障碍物，然而，用传感器B测量时，第一次测量距离比第二次测量距离小，这就表明向右转才能到达湖岸。 第三种情况是：通过A传感器第一次和第二次测量的距离超出了额定范围，而采用B传感器测量时，第一次测量距离要大于第二次测量距离，这时候表明向左转就可以抵达湖岸边，（参见图3 time4）。最后一种情况是：采用传感器A的测量值不到2m，但是采用传感器B测量时，测量值是相同的。在这种情况下，障碍可能存在于清扫船前或者湖岸边直角方向向左。（参见图3 time5）电机将控制相应的功能使船在湖岸边移动。 图3 清扫船运动控制策略 D：避开障碍物系统设计 当清扫船在湖泊上行驶时，清扫船可能会遇到障碍物，因此有可能它就会自动地避开障碍物，然后回到原来的行驶轨道。是否存在障碍在两次超声波测量的距离之内，遇到障碍物或者在清扫船前面选择靠近湖岸边在方法上是与决定直角向左转的方法是相似的。这也就是说通过传感器A测量的距离是2m和通过传感器B测得的距离是一样的。在这种情况下，遇到障碍或者靠岸这两种情况应该事先被考虑，所以这艘清扫船应该被控制直角左转（参见图4 time1）。当使用传感器A测得的距离值大于3米并且采用传感器B测得的距离值是60厘米时，船舶开始直线行走。如果清扫船从直角向左转时，用传感器B测得的距离值不会改变的(参见图4 time 5)，如果清扫船遇到障碍，采用传感器B测得的距离会比之前测得的距离大，因为障碍是长方形的或者是弧形的。因此船会向右转（请见图4 time3）。直到采用传感器B测得的距离是60厘米，这个时候清扫船会直着行驶。当探测到要靠近湖岸边的时候，清扫船将会在直角区域内向左转（请见图4 time3）。最后由于用传感器A测得的距离值大于3米并且采用传感器B测得的距离值是60厘米，清扫船回到自己的特定轨道。 图4 ：避开障碍物船的战略设计 E: 辨别白天或者黑夜的电路设计 使用一个在不同的关照强度条件下，有不同的电阻值的光敏电阻，该系统能够识别白天或者黑夜。当光线较强时，电阻值较小。相反，在光线较弱时，电阻值反而很大。在辨别电路中，固定电阻器和光敏电阻器是用来区分固定电压和被采用的参考电压的。电压比较器是用来确定输出电压的，如果被划分的电压比参考电压小时，白天和夜间的识别系统会会决定它是在夜间，否则被认为在白天。在白天时，可以设置清洗循环频率，而在夜间清扫船只循环一次。 F：电机控制系统设计 清扫船的动力包括垃圾收集传送带和传动装置，传输装置和垃圾存储装置都具有一定的独特设计。还有驱使清扫船行驶和灵活地变更方向的两个螺旋桨。这些装置全都是直流电机供能的。两高速直流电机用于驱动两个螺旋桨，并且编号为TA8050P专用集成电路用于控制驱动齿轮箱皮带传动的电机。五种控制方案的设计包括：直走，左转弯，右转弯，直角弯左转，直角弯右转。当两个高速电机速度控制以同样的速度运转时，清扫船要直线行驶。当右边电机加速时，清扫船将会左转。当左边电机的速度保持不变时，这时清扫船会向右转，而且会有较大的转弯半径。当左侧电机停止转动，右侧电机保持原来速度行驶，这时清扫船在直角转弯时将会向左转。相反的情况下，清扫船将会在直角转弯向右转。 G：遥控系统设计 除了键盘和显示电路，遥控系统的设计也实现了手动控制清扫船的效果。无线电频信号可以辐射四周并且中间不可有障碍物抵挡，是作为航空公司运输远程控制消息。遥控器可以控制距离达到500米的船，它有8个按键，手动模式和自动模式之间的切换键、控制移动方向键、控制驱动传送带的电机键。 H：供电系统设计 控制系统需要一个12伏电源，主要用来驱动超声波发射器和直流电机。它还需要一个用于供电的单片机控制系统的5伏电源。动力来自太阳能输出的额定功率15瓦，用来收取一个12伏/7AH免维护铅酸蓄电池。后者是用于电力系统。充电过程中，电池电压是被电力系统监控的避免过放电和过充电。对于单片机的5伏的电源由一三稳压器稳压，为了避免电动机起动停止操作影响控制电路，直流与直流功率电路的设计是为了提供电源隔离。 I:程序设计 根据清扫船的工作过程，主要的SCM系统的程序和距离测量系统是模块化结构设计。供应链管理系统的程序的主要包含以下模块:项目管理电力系统,远程控制的程序,距离测量程序交流，控制移动方向程序，控制电机程序。图5可以显示供应链管理系统流程图，这两个从动装置的单片机系统的主要工作是实现超声波测距和发送到主机的测量距离串行通信。 图5：掌握单片机的流程图 工作过程如下：首先是电池能量的检测，如果电压低于阀值，这时候船将会停下来，一个低能信号将通过LED闪过灯发出信号，如果电源电压是正常的，它会检查是否有按键被按下。被设计的键盘可以设定清扫船的清洗循环频率，如果工作模式是自动的，相应的LED灯也会自动显示工作状态。之后，系统会检查是否有从动装置的单片机系统发出数据和接受数据。接收到的数据将会有主计算机系统计算控制。如果这艘船在手动模式下工作，它将显示手动状态，并执行控制清扫船按照键盘的按键的遥控器。 III. 清扫船的试验性研究 我们已经进行了试验，包括超声波测距，手动操作和自动操作测试。与标准的机械测量表相比，超声波的测量精度约为1厘米时，测量距离则在25厘米和300厘米之间，自船舶运行路径周围形成的基础上测量距离,船不能离开远离湖的岸边。实验表明,该传感器实现清扫船的运行过程。对于清扫船的运行不需要跟高精度。此外，这艘清扫船可以通过手动或自动方式实现向左转，向右转，直行，直角弯左转，直角弯右转。并且能够成功执行检测障碍物和避开障碍物这种功能。然而，仍存在一些不足之处。一方面，这艘船的功能比较先进。另一方面，如果湖的岸边曲率半径较大时，船首先还是会慢慢地向左转弯，然后再慢慢地直角向左转。这时就有可能这艘船会撞到岸边。因此，清扫船行驶的道路可能不是一帆风顺。 IV. 结束语 在这篇文章中，主要是根据湖面漂浮物垃圾的结构和工作原理提出了垃圾清扫船。而且清扫垃圾船既可以通过手动方式来实现运动又可以通过自动方式达到目的。同时也提出了超声波测距的方法。通过对湖面上的漂浮物垃圾的分布特征进行分析，提出一种方法清扫湖岸周围的湖面漂浮垃圾。两个超声波测距系统主要是用来获取定位的，第一定位是清扫船的方向，第二定位是清扫船的位置定位。只有在五种情况下才被编程，这艘船的运动路径不是很顺利。在更多的情况基础上分析，以上五种情况可以使船的行驶情况更完美，更平行于湖岸边。实验已经证明，自动清扫湖面上漂浮物垃圾船的设计是非常适用的。经过这样的分析设计我们将会得到一艘可以自动避开障碍物，并且能够打捞湖面上的漂浮垃圾。这样在效率上，就会比以前的人工打捞既省力又省时。另外，我们可以在一些恶劣天气下照常可以完成操作，因为这艘垃圾清扫船不仅可以通过手动方式完成清扫情况，而且也可以通过自动方式达到目的。这艘船的到来，在今后应该会给我们带来很多方面，我们就能引用干净的水源，以及我们的水源得到良好的保护。一些动植物也能很好地生存下来。今后，应该会有个翻天覆地的变化，会让我们看不到成片成片的垃圾漂浮在湖泊以及河道的水面上。 主要参考资料 [1] 黎启柏，肖长周;水面垃圾打捞机械手及其液压驱动系统;华南理工大学学报(自然科学版);1996年02期 [2]天津海河漂浮物调查 [3] 贾秀杰;多功能全自动抓取器的应用; 新技术新工艺;1999年04期 [4] 张玉新;王帅;水面垃圾清理船的仿真设计与研究; ];机械设计与制造;2011年04期 [5]浸水装置，水力学以及气体力学 [6]袁胜发;许德昌;谭桂斌;王柏雨;气动式水面垃圾清理装置的研究;液压与气动;2008年12期 附录二：An Autonomous Ship for Cleaning the Garbage Floating on a Lake Abstract—Water pollution with floating garbage is getting more and more serious in many countries. The design of an autonomous ship for cleaning the garbage floating on a lake has been proposed. The ship is powered by a solar battery. Circuit for protection of the excessive charge and discharge of the battery system has been used. Ultrasonic sensors have been equipped to detect the distance between the ship and the bank of the lake. The position and the orientation of the ship can be determined by measuring the distance between the ship and the bank at two successive time, which is used for controlling the running direction of the ship to make the ship autonomously run in an annular zone of a short distance away from the bank. The ship has also been equipped with a system to detect the occurrence of obstacles and to bypass the detected obstacles. Two screw propellers have been installed at the two sides of the ship to drive the ship, which makes the ship change its direction nimbly. A photo-resistance has been used to determine if it is in daytime or nighttime. The ship circulates the lake only one time at nighttime to save power energy. Wireless remote control is also available, which makes the ship user friendly. Experiments have demonstrated the applicability of the design。 Keywords: autonomous; floating garbage; ultrasonic; cleaning ship; pollution I. INTRODUCTION Natural lakes and all kinds of artificial lakes make the living environment beautiful. However, with the increase of the activities of human being, the pollution of the floating garbage on the surface of the lake is more and more serious. Governing the pollution of the floating garbage on the surface of the lake is more and more urgent [1]. It can be seen by observation that the velocity of the water flow in the lake is very low. Sometimes it is almost zero. Most of the floating garbage distribute over an area near the bank of the lake [2]. At present, almost all these floating garbage is cleaned manually [3], which is time consuming, expensive in cost, and low in efficiency. To solve the abovementioned problem, we have designed an autonomous ship for cleaning the garbage floating on a lake. As shown in Fig.1, a model ship has been developed. Experiments have been conducted to demonstrate the applicability of the design. II. DESIGN OF THE CLEANING SHIP The cleaning ship is powered by solar battery, which is economic, and can save energy and protect environment. The cleaning ship determines the position and the direction of it’s own by taking the lake bank as the frame of reference. The ship runs around the lake bank by controlling itself running in a predefined distance away from the lake bank. At the same time, it automatically cleans the floating garbage. The ship can change direction if the equipped ultrasonic sensors have detected obstacles. Circuits for recognizing the daytime and the nighttime are designed too. The ship runs only once at nighttime to save electric energy. The circulating times of cleaning floating garbage at daytime can be determined according to the practical environment. A remote control circuit is designed, which makes manual control of the ship applicable. This is useful in some special circumstances, and thus can increase the practicability of the ship. A mechanism for collecting floating garbage is designed to realize automatic collecting floating garbage. To realize the functions mentioned above, the designed cleaning ship should be controlled by a microprocessor. It should also have power supply system, keyboard and display, obstacles detecting system, ship position and orientation detection system, motion controlling system, circuit for recognizing daytime and nighttime, and remote control system, as can be seen in Fig.2. Figure 2. The structure of the cleaning ship A. Design of the single-chip microcomputer (SCM) system The main SCM system of the cleaning ship is made up of a SCM, a crystal oscillator, a watchdog timer. The SCM is AT89S52, produced by Atmel Corporation. It features 8k bytes of on-chip flash memory, 256 Bytes of on-chip RAM, two 16-bit timers/counters, two external interrupt, and one full duplex UART .The oscillating frequency of the SCM is 12 MHz. The Watchdog timer reset the computer system on power up, power failure, and other abnormity. The Watchdog circuit is MAX813, produced by Maxim Corporation, which is dedicated to production of integrated circuits for power-detection and Watchdog timer B. Design of the keyboard and display module ZLG7289 has been applied in both the keyboard circuit and the display circuit in our cleaning ship, which was produced by Zhouligong Corporation situated in Guangzhou. A ZLG7289 chip can drive 7-segment numeric LED displays of up to 8 digits, bar-graph displays, or 64 individual LEDS, and a keyboard of up to 64 keys. It communicates with the SCM through the serial peripheral interface (SPI) [4], which takes only three I/O pins of the SCM to save its limited resources. The key pin of the ZLG7289 becomes low when a key is pressed. The SCM identifies the number of the keystroke by SPI bus when reading the low level signal. There are eight 7-segment numeric LED displays and six keys. 7-segment numeric LED display the distance value obtained from the distance-detection system. Six function keys are used for setting the control parameters of the cleaning ship. C. Design of the motion control system The motion control system controls the cleaning ship to move in a lake. Two slave systems detect the distances between the bank and the cleaning ship, and sent the distance values to the main control system through the asynchronous serial port. The main control system determines the position and orientation of the cleaning ship according to the two distance values. Ultrasonic range sensors are used to measure the distance in the system. Ultrasonic ranging is a method that uses reflective ranging method [5]. The distances to be measured are calculated according to the time period between the time at which the system transmits ultrasound waves and that at which the system receives the echo. Every ranging system is controlled by an independent SCM to transmit the ultrasound and to receive its echo [6]. The dedicated integrated circuit LM1812 fulfills the task of transmitting ultrasound waves. While the task of receiving the echo is fulfilled by the infrared receiver module CX20106. When the control signal of the transmission of the ultrasound is sent, the internal timer of the SCM is being started at the same time. The integrated circuit CX20106 will send a low-level signal through which the external interrupt of the SCM is triggered to stop the timer when the echo is received. The distance between the ship and objects can be calculated from the data in the timer. The ship is equipped with two ultrasonic ranging systems. One of which is at the front of the ship, marked as “A”. Another is placed at the ship’s right side, marked as “B”. The two sensors measure the distance between the ship and the bank of the lake once every two seconds. The position and orientation of the ship relates to the bank of the lake are determined according to the distances at two successive times. There are several different situations as described in the following The first situation is that the distances measured by A at both the first and the second times are over range. That is to say that the distance is more than 3 meters. And the distances measured by B are the same, about 60 centimeters, at this time, the ship is considered to be parallel to the bank of the lake, (see Fig. 3 time 2). The second situation is that the distances measured by A at both the first and the second times are over range. Therefore, there are no obstacles in front. However, the first distance measured by B is smaller than the second one, which suggests that the bank turns to the right, (see Fig.3 time 3). The third situation is that the distances measured by A at both the first and the second times are over range. While the first distance measured by B is lager than the second, which suggests that the bank turns to the left, (see Fig.3 time 4). The last situation is that the distances measured by A are less than two meters while the distances measured by B are the same. In this situation, obstacles may exist in front of the ship or the bank takes a right-angle turn to the left (see Fig.3 time 5). The motors will be controlled correspondingly to make the ship move around the bank of the lake. Figure 3. Ship motion control strategy D. Design of the bypassing obstacles system When moving in the lake, the cleaning ship may encounter obstacles. Therefore, it should be able to automatically bypass obstacles, and then return to its original orbit. Whether there exist obstacles or not is determined based on the data the two ultrasonic sensors measured. The preliminary decision of an obstacle or a turning of the bank in front of the ship is similar to the method for deciding the right-angle turn to the left. That is to say that the distances measured by A are two meters, and the distances measured by B are the same. In this situation, an obstacle or a turning of the bank is considered to be in the front, and therefore the ship should be controlled to make a right-angle left turn (see Fig.4 time 1). When the distances measured by A are larger than 3 meters and the distances measured by B are 60 centimeters, the ship starts to go straightly. If the ship has made a right-angle turn to the left, the distances measured by B will not change (see Fig.4 time 5).If the ship has encountered an obstacle, the distances measured by B will become bigger than the distances measured before. The reason is that obstacles are arc-shaped or rectangular-shaped. The ship will turn to right accordingly (see Fig.4 time 3). Not until that the distances measured by B are 60 centimeters, will the ship go straight. The ship will turn left at right angles after the bank of the lake is detected (see Fig.4 time 3). Finally, the ship will go back to the confined orbit as the distances measured by A are lager than 3 meters and the distances measured by B are 60 centimeters. Figure 4. Strategy for the ship to bypass an obstacle E. Design of the circuit for recognizing daytime/nighttime Using a photosensitive resistance, which will have different resistance values under different light intensity, the system is able to recognize daytime and nighttime. When light is strong, its resistance value is small. On the contrary, resistance value will increase at low light. In the recognizing circuit, fixed resistors and photosensitive resistor are used to divide up the fixed voltage, and referenced voltage has been adopted. A voltage comparator is used to determine the output voltage. If the voltage divided up is smaller than the referenced voltage, the recognizing daytime and nighttime system determines it is at nighttime, otherwise it is considered at daytime. During the daytime, the frequency of the cleaning circulation can be set. While at nighttime, the cleaning ship circulates only one time. F. Design of the motor control system The power of the cleaning ship, including the conveyor belt of the refuse collection and transmission, and the two propellers which drive the ship and change its direction nimbly, are all powered by DC motors. The two high speed DC motors used to drive two propellers, and the motor used to drive the conveyor belt with gear case, are all controlled by special ICs Numbered TA8050P. Five controlling scenarios are designed which include going straight, turning to the left, turning to the right, turning to the left at rightangle and turning to the right at right-angle. The speeds of the two high-speed motors are controlled running at the same speed when the ship is going straight. The ship is turning left when the right side motor speeds up while the speed of the left side motor remains unchanged The left side motor speeds up while the speed of the right side motor keeps unchanged will lead to the ship turning right, which can result to a larger turning radius. The ship is turning left at right angle when the left side motor stops while the right side motor runs at the original speed. In the opposite situation, the ship is turning right at right angle. G. Design of the remote control system Besides the keyboard and display circuit, the remote control system is also designed to achieve manual control of the cleaning ship. Radio frequency signal, which can be radiated around and cannot be warded off by obstacles, is used as carriers to transport the remote control message. The remote controller can control the ship in a distance of up to 500 meters. It has 8 keys, including the key to switch between the manual mode and automatic mode, the keys to control the moving directions, and the key to control the motor that drives the conveyor belt. H. Design of the power supply systems The control system needs a 12-volt power supply, which is used for powering the ultrasonic transmitter and the DC motors. It also needs a 5-volt power supply used for powering the single-chip control system. The power comes from a solar battery of 15Watts rated output, which is used to charge a 12V/7AH maintenance-free lead acid battery. The latter is then used to power the system. During charge process, the battery voltage is monitored by the power system to avoid overcharge and over-discharge. The 5-volt power supply for the SCM is stabilized by a three-terminal voltage regulator. In order to avoid the motor starting/stopping operations influencing the control circuit, a DC-DC power conversion circuit is designed for power supply isolation. I. Design of programs According to the process of the work of the cleaning ship, the programs of the main SCM system and distance measurement systems are designed in a modular structure. The programs of the main SCM system consist of the following modules: the program for managing the power system, the program for the remote control, the program for communicating with slave distance measurement systems, the program for controlling the moving directions, and the program for controlling the motors. The flow chart of the main