MechanicalDesignProcess << Previous Next >> assignment3

Keyboard control car

V-rep 馬達驅動四輪車

剛開始可以使用內建的功能來創建模型，Add > Primitive shape > Cuboid(需要的形狀)，給定所需形狀的參數值即可，創建出一個正方形本體，還有四個圓柱形輪子，移動到相對應的位置，再來加上馬達 Add > Joint > Revolute，分別定位在四個輪子的軸上，雙擊Revolute_joint圖示，在彈出的屬性框點擊Show dynamic parameters dialog，勾選 Motor enable，並設置 Target velocity 為 10，四個馬達都是如此。

影片連結:https://youtu.be/y8DJ1sjuAqM

四輪車鍵盤控制轉向

V-rep 檔案連結: 4 wheel car keyboard.ttt

四輪車加上轉向及鍵盤控制，先開啟之前做好的四輪車，將兩個前輪馬達複製貼上，再使兩個馬達原地轉向90度，創建兩個小正方體，位置與前輪一模一樣，需要設定屬性避免與其他部件衝突，本體、輪子、小正方體都要關閉如下圖。

將控制迴路啟用，來控制轉向的限制角度，兩個馬達都用預設即可，如下圖設定。

將之前的馬達速度都關掉，點擊馬達圖示視窗下的show dynamic properties dialog，把motor properties的速度改為0，底下的lock motor when target velocity is zero是馬達速度為零時鎖定馬達，可開可不開。

最後把方塊拖移至對應馬達下，再整個放進本體下，把對應的前輪馬達放置方塊下，本體新增一個控制腳本，選擇cuboid，點擊菜單欄的Add > Associated child script > Threaded，將寫好的腳本複製貼上，更改前輪馬達的名子，這樣腳本才能控制，下圖為整個最終結構。

四輪車鍵盤控制轉向程式碼:

-- This script is threaded! It is a very simple example of how Ackermann steering can be handled.
-- Normally, one would use a non-threaded script for that
 
threadFunction=function()
    while simGetSimulationState()~=sim_simulation_advancing_abouttostop do
        -- Read the keyboard messages (make sure the focus is on the main window, scene view):
        message,auxiliaryData=simGetSimulatorMessage()
        while message~=-1 do
            if (message==sim_message_keypress) then
                if (auxiliaryData[1]==2007) then
                    -- up key
                    desiredWheelRotSpeed=desiredWheelRotSpeed+wheelRotSpeedDx
                end
                if (auxiliaryData[1]==2008) then
                    -- down key
                    desiredWheelRotSpeed=desiredWheelRotSpeed-wheelRotSpeedDx
                end
                if (auxiliaryData[1]==2009) then
                    -- left key
                    desiredSteeringAngle=desiredSteeringAngle+steeringAngleDx
                    if (desiredSteeringAngle>45*math.pi/180) then
                        desiredSteeringAngle=45*math.pi/180
                    end
                end
                if (auxiliaryData[1]==2010) then
                    -- right key
                    desiredSteeringAngle=desiredSteeringAngle-steeringAngleDx
                    if (desiredSteeringAngle<-45*math.pi/180) then
                        desiredSteeringAngle=-45*math.pi/180
                    end
                end
            end
            message,auxiliaryData=simGetSimulatorMessage()
        end
 
        -- We handle the front left and right wheel steerings (Ackermann steering):
        steeringAngleLeft=math.atan(l/(-d+l/math.tan(desiredSteeringAngle)))
        steeringAngleRight=math.atan(l/(d+l/math.tan(desiredSteeringAngle)))
        simSetJointTargetPosition(steeringLeft,steeringAngleLeft)
        simSetJointTargetPosition(steeringRight,steeringAngleRight)
 
        -- We take care of setting the desired wheel rotation speed:
        simSetJointTargetVelocity(motorLeft,desiredWheelRotSpeed)
        simSetJointTargetVelocity(motorRight,desiredWheelRotSpeed)
 
        -- Since this script is threaded, don't waste time here:
        simSwitchThread() -- Resume the script at next simulation loop start
    end
end
 
-- Put some initialization code here:
-- Retrieving of some handles and setting of some initial values:
steeringLeft=simGetObjectHandle('Steer_left_joint')
steeringRight=simGetObjectHandle('Steer_right_joint')
motorLeft=simGetObjectHandle('Front_left_joint')
motorRight=simGetObjectHandle('Front_right_joint')
desiredSteeringAngle=0
desiredWheelRotSpeed=0
steeringAngleDx=2*math.pi/180
wheelRotSpeedDx=20*math.pi/180
d=0.755 -- 2*d=distance between left and right wheels
l=2.5772 -- l=distance between front and read wheels
 
-- Here we execute the regular thread code:
res,err=xpcall(threadFunction,function(err) return debug.traceback(err) end)
if not res then
    simAddStatusbarMessage('Lua runtime error: '..err)
end
 
-- Put some clean-up code here:

教學影片連結:https://youtu.be/0W1wmC1tr4A

MechanicalDesignProcess << Previous Next >> assignment3