lua实现PID算法

工作需要，搜遍网络，但没有现成的，故自行解决，秉承开源之原力，

有不足之处，诸君海涵

--[[结构体：]]

local pid_struct = {pv=0.0,sp=0.0,integral=0,
        pgain=1.5, igain=0.1,dgain=0.0,
        deadband=1.0,last_error=0.0,
        max_value=50.0,min_value=30.0,
        stable_time=1, modify_time=current};

--[[计算PID函数]]

function pid_calc(pid)
    local err;
    local pterm;
    local dterm;
    local result;
    local ferror;
    err = (pid.sp) - (pid.pv);


    if (math.abs(err) > pid.deadband) then
        ferror = err;

        pterm = pid.pgain * ferror;

        if (pterm > 100 or pterm < -100) then
            pid.integral = 0.0;
        else

            pid.integral = pid.integral + pid.igain * ferror;

            if (pid.integral > 3.0) then
                pid.integral = 3.0;
            end
            if (pid.integral < -3.0) then
                pid.integral = -3.0;
            end
        end

        dterm = (err - pid.last_error) * pid.dgain;
        result = pterm + pid.integral + dterm;
    else
        --进入死区
        result = pid.integral;
    end

    result = pid.sp + result;

    --极值限制
    if(result > pid.max_value) then
        result = pid.max_value;
    end
    if(result < pid.min_value) then
        result = pid.min_value;
    end

    return result;

end