我有一台静止模式的机器。当它开始运行时,它的频率线性变化(从0到完全工作频率),然后变得恒定,最后开始线性减少(从完全工作频率到0)。
为此,我编写了以下代码:
te = 300; % seconds - time to get fully operative
% (to arrive from 0 to fully operational frequency)
% and to stop (from fully operational to 0)
me = 10; % eccentric mass
e = 0.5; % eccentricity of the eccentric mass
omega=0.2; % fully operational force frequency
% i need three time vectors
tt0=[0:0.1:te]; % uphill frequency part (from 0 to fully operational frequency)
tt1=[te+0.1:0.1:1.5*te]; % permanent fully operational frequency part
tt2=[1.5*te+0.1:0.1:2.5*te]; % downward frequency part (from fully operational frequency to 0)
tt_1=[tt0,tt1,tt2]; % whole time vector
n7=numel(tt_1);
n5=numel(tt0);
n6=numel(tt1);
n8=numel(tt2);
% create a 3 force frequency vectors
delta_omega1=omega/(n5-1);
delta_omega2=omega/(n8-1);
omega000=[0:delta_omega1:omega]; % from 0 to fully operational frequency
omega001=omega*ones(1,n6); % permanent fully operational frequency part
omega002=[omega:-delta_omega2:0]; % from fully operational frequency to 0
omega00=[omega000,omega001,omega002]; % whole force frequency vector
p00=zeros(n7,1);
p_0010=zeros(n5,1);
p_0011=zeros(n6,1);
p_0012=zeros(n8,1);
p_001=zeros(n7,1);
% force amplitude calculation
for j=1:n7
p00(j,1) = (me*e*omega00(j)^2);
end
% then i create 3 sin force vectors (for 3 different force frequency laws)
for j=1:n5
p_0010(j,1) = p00(j,1)*sin(omega/(2*te)*(tt0(j))^2);
end
for j=1:n6
p_0011(j,1) = p00(j+n5,1)*sin(omega*te+omega*(tt1(j)-te));
end
for j=1:n8
t2=tt2(1);
p_0012(j,1) = p00(j+n6+n5,1)*sin((-1/2*omega*te+omega*tt2(j)-...
1/2*omega/te*((t2-te)^2+(tt2(j)-t2)^2)));
end
p_001=[p_0010;p_0011;p_0012]; % whole force vector
figure (1)
plot (tt_1,omega00)
xlabel('time')
ylabel('force frequency')
grid on;
hold on
figure (2)
plot (tt_1,p_001)
xlabel('time')
ylabel('applied force')
grid on;
hold on
这导致了
这是正确的。
但力图:
是不正确的。
我怎么才能解决这个问题呢?我不需要力图上的任何不连续(因为它会使我的系统产生奇怪的行为,就像这个奇点上的“寄生虫共振”)。
1条答案
按热度按时间fnatzsnv1#
你对力的表述是错误的。对于不平衡力,只有当转速omega恒定时,它的表达式才是
me*omega^2*sin(omega*t)
。如果转速不是恒定的(就像它线性增加或减小的情况一样),则其完整表达式为对于旋转机械,你应该在水平和垂直方向上有不平衡力(上面的力矢量上的第二和第三项)。δ为相角,ϕ_DOT为转速,ϕ_DDOT为旋转加速度。请注意,对于线性增大或减小的转速,ϕ_ddot=α=Constant,因此力表达式应该包含一个项
α*cos(phi)
对于恒定加速度,Angular 位置正如您定义的那样。只需正确定义每个时间间隔的初始角位置
phi_0
(它们不是零,它们是前一个时间间隔的最后位置)。