PID增益计算：广义最小方差控制律设计

/\n Compute a set of PID gains using General Minimum Variance Control law design\n*\n* @param num: the coefficients of the numerator of the discrete-time plant transfer function\n* @param den: the coefficients of the denominator of the discrete-time plant transfer function\n* @param dt: the sampling time in seconds\n* @param sigma: the desired closed-loop rise time in seconds\n* @param delta: the damping index (between 0 and 2). 0 is critical damping, 1 is Butterworth\n* @param lbda: the "detuning" coefficients. This affects the gain of the controller kc only (increase to detune the controller)\n*\n* @return The PID gains in standard form: u = kc*[1 + kidt + kd/dt]e\n kc: the controller gain\n ki: the integral gain (= 1/Ti)\n* kd: the derivative gain (= Td)\n*\n* Reference:\n* T.Yamatoto, K.Fujii and M.Kaneda, Design and implementation of a self-tuning pid controller, 1998\n*/\n函数功能内容：计算使用广义最小方差控制律设计的PID增益。\n\n函数参数:\n- num：离散时间传递函数的分子系数\n- den：离散时间传递函数的分母系数\n- dt：采样时间，以秒为单位\n- sigma：期望的闭环上升时间，以秒为单位\n- delta：阻尼指数（介于0和2之间）。0表示临界阻尼，1表示巴特沃斯阻尼\n- lbda：“失调”系数。这影响控制器增益kc的值（增加以减小控制器的失调）\n\n返回值：\n以标准形式表示的PID增益：u = kc*[1 + ki*dt + kd/dt]*e\n- kc：控制器增益\n- ki：积分增益（= 1/Ti）\n- kd：微分增益（= Td）\n\n参考文献：\nT.Yamatoto, K.Fujii and M.Kaneda, Design and implementation of a self-tuning pid controller, 1998