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本文为在用龙芯1c做3D打印机过程中的笔记。龙芯1c做的3d打印机简称“龙印”，Git地址“https://gitee.com/caogos/marlin_ls1c”
网上pid的资料很多，但展示整定全过程的视频不多。这里以龙芯1c的智龙开源主板+ramps1.4扩展板实现的3D打印机用pid控温为例，以程序员的角度整定pid，在大致确定温度采样周期和控制加热装置的pwm周期后，主要通过调节比例项、积分项、微分项和维持功率项的系数来将温度控制在指定范围。
温度采样周期的选择：以在温度快速变化时，相邻两次或三次采集的温度有变化，变化又不至于太大为宜。这句话怎么理解，首先温度变化从微观上讲并不是曲线，而是梯形，这个不会随温度采样周期的大小而改变。如果采用周期太小，则会看到连续采样几次的值都是一样的，采样周期太大，则会发现相邻两次的温度变化太大，这个根据实际情况选择一个合适的值。比如，我把温度采集周期设置为500ms，即每秒采集两次。
加热装置的pwm周期的选择：加热装置的pwm周期最好不要大于温度采集周期，否则温度采集后，计算得到的pid值，不能很好的传递给加热装置执行。即加热装置还未执行完上一次pid计算得到的结果，又有一个新的pid值需要执行。个人认为加热装置的pwm周期小于或等于温度采集周期的一半比较合适。比如，我把加热头的pwm周期设为200ms。温度采集周期一旦确定，那么pid的微分时间就确定了。
pid的积分时间通常由代码确定，即当前温度与目标温度相差n度时才开始积分，当温度超过这个限定后将积分项清零，待又回到区间内时重新积分。还可以为积分作用加些保护措施。
所以本文主要调节pid系数，而非积分时间，微分时间。但是以正确温度采集周期和加热装置的pwm周期为前提，一旦温度采集周期或加热装置的pwm周期改变了，应该重新检查之前的pid系数是否还合适。
cpu：龙芯1c
主板：智龙
扩展板：开源3d打印机扩展板ramps1.4（主要用了其中的STP55NF06L控制加热头）
温度采集：热敏电阻+AD芯片TM7705
在linux上实现的。其中的文章之前已经写了，控制加热头的pwm也是linux驱动中的软件定时器模拟的，这里重点关注pid算法和整定过程。完整的代码在http://git.oschina.net/caogos/marlin_ls1c
/* * include\linux\ls1c_3dprinter_heater_fan.h * 3d打印机加热头和风扇(散热)驱动的头文件 */#ifndef MY_LS1C_3DPRINTER_HEATER_FAN_H#define MY_LS1C_3DPRINTER_HEATER_FAN_H// 挤出机加热头的gpio#define PRINTER_EXTRUDER_HEATER_PIN (90) // I2S_BCLK/GPIO90// 挤出机散热风扇的gpio#define PRINTER_EXTRUDER_FAN_PIN (91) // I2S_MCLK/GPIO91struct platform_3dprinter_heater_fan_data { unsigned char extruder_heater_gpio; // 挤出机加热头的gpio unsigned char extruder_fan_gpio; // 挤出机散热风扇的gpio};#endif /* * drivers\misc\ls1c_3dprinter_heater_fan.c * 3d打印机加热头和风扇(散热)驱动 * 用linux内核定时器模拟pwm */ #include#include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include // pwm周期(ms)#define HEATER_FAN_PWM_TIME_MS (200) // 200msenum{ HEATER_NOT_WORK = 0, // 不加热(加热装置不工作) HEATER_WORK = 1, // 加热(加热装置正常工作)};enum{ FAN_NOT_WORK = 0, // 不散热(风扇不工作) FAN_WORK = 1, // 散热(风扇正常工作)};// 一个pwm周期内，工作的时长，单位ms// 由于驱动中不能进行浮点计算// 所以在应用程序中将pid的占空比直接换算为一个周期内加热头和散热的风扇工作的时长typedef struct{ unsigned int extruder_heater_ms; // 挤出机加热的时长(ms) unsigned int extruder_fan_ms; // 挤出机风扇工作的时长(ms)}heater_fan_work_time_t;static heater_fan_work_time_t heater_fan_work_time = {0};static struct platform_3dprinter_heater_fan_data *heater_fan_data = NULL;// 用于模拟pwm的定时器static struct timer_list extruder_heater_timer; // 挤出机加热的定时器static struct timer_list extruder_fan_timer; // 挤出机散热风扇的定时器static DEFINE_MUTEX(heater_fan_lock);// 给挤出机加热static void extruder_heater_enable(void){ gpio_direction_output(heater_fan_data->extruder_heater_gpio, HEATER_WORK);}// 挤出机不加热static void extruder_heater_disable(void){ gpio_direction_output(heater_fan_data->extruder_heater_gpio, HEATER_NOT_WORK);}// 给挤出机散热static void extruder_fan_enable(void){ gpio_direction_output(heater_fan_data->extruder_fan_gpio, FAN_WORK);}// 不给挤出机散热static void extruder_fan_disable(void){ gpio_direction_output(heater_fan_data->extruder_fan_gpio, FAN_NOT_WORK);}// 挤出机加热定时器中断(模拟pwm)void extruder_heater_timer_timeout_fn(unsigned long arg){ static int level = 0; // 判断是否需要加热 if (0 == heater_fan_work_time.extruder_heater_ms) { // 不需要加热 extruder_heater_disable(); mod_timer(&extruder_heater_timer, jiffies + HEATER_FAN_PWM_TIME_MS); level = 0; return ; } // 是否在整个pwm周期内一直加热 if (HEATER_FAN_PWM_TIME_MS <= heater_fan_work_time.extruder_heater_ms) { // 一直加热 extruder_heater_enable(); mod_timer(&extruder_heater_timer, jiffies + HEATER_FAN_PWM_TIME_MS); level = 0; return ; } // 模拟pwm if (0 == level) { level = 1; extruder_heater_enable(); mod_timer(&extruder_heater_timer, jiffies + heater_fan_work_time.extruder_heater_ms); } else { level = 0; extruder_heater_disable(); mod_timer(&extruder_heater_timer, jiffies + (HEATER_FAN_PWM_TIME_MS - heater_fan_work_time.extruder_heater_ms)); } return ;}// 挤出机散热风扇定时器中断(模拟pwm)void extruder_fan_timer_timeout_fn(unsigned long arg){ static int level = 0; // 判断是否需要散热 if (0 == heater_fan_work_time.extruder_fan_ms) { // 不需要散热 extruder_fan_disable(); mod_timer(&extruder_fan_timer, jiffies + HEATER_FAN_PWM_TIME_MS); level = 0; return ; } // 判断是否在整个pwm周期内一直散热 if (HEATER_FAN_PWM_TIME_MS <= heater_fan_work_time.extruder_fan_ms) { // 一直散热 extruder_fan_enable(); mod_timer(&extruder_fan_timer, jiffies + HEATER_FAN_PWM_TIME_MS); level = 0; return ; } // 模拟pwm if (0 == level) { level = 1; extruder_fan_enable(); mod_timer(&extruder_fan_timer, jiffies + heater_fan_work_time.extruder_fan_ms); } else { level = 0; extruder_fan_disable(); mod_timer(&extruder_fan_timer, jiffies + (HEATER_FAN_PWM_TIME_MS - heater_fan_work_time.extruder_fan_ms)); } return ;}static int heater_fan_open(struct inode *inode, struct file *filep){ int hz = HZ; printk(KERN_DEBUG "[%s] HZ=%d, 1000 is expected.\n", __FUNCTION__, hz); return 0;}static int heater_fan_close(struct inode *inode, struct file *filep){ // 停止挤出机的加热和风扇 extruder_heater_disable(); extruder_fan_disable(); heater_fan_work_time.extruder_heater_ms = 0; heater_fan_work_time.extruder_fan_ms = 0; return 0;}static ssize_t heater_fan_write(struct file *filp, const char __user *buf, size_t count, loff_t *offp){ heater_fan_work_time_t work_time = {0}; if (sizeof(heater_fan_work_time_t) != count) { // 写入额数据不对 return 0; } if (mutex_lock_interruptible(&heater_fan_lock)) { return -ERESTARTSYS; } copy_from_user(&work_time, buf, sizeof(heater_fan_work_time_t)); heater_fan_work_time.extruder_heater_ms = work_time.extruder_heater_ms; heater_fan_work_time.extruder_fan_ms = work_time.extruder_fan_ms; mutex_unlock(&heater_fan_lock); return 0;}static struct file_operations ls1c_heater_fan_ops = { .owner = THIS_MODULE, .open = heater_fan_open, .release = heater_fan_close, .write = heater_fan_write,};static struct miscdevice ls1c_heater_fan_miscdev = { .minor = MISC_DYNAMIC_MINOR, .name = "3dPrinter_heater_fan", .fops = &ls1c_heater_fan_ops,};static int heater_fan_probe(struct platform_device *pdev){ int ret = 0; printk(KERN_INFO "ls1c 3dprinter heater fan driver's build time %s %s\n", __DATE__, __TIME__); heater_fan_data = pdev->dev.platform_data; if (!heater_fan_data) { dev_err(&pdev->dev, "failed to find platform data\n"); return -EINVAL; } // 挤出机加热头 ret = gpio_request(heater_fan_data->extruder_heater_gpio, "ls1c_3dPrinter_heater_fan"); if (0 > ret) { printk(KERN_ERR "[%s] request extruder heater gpio fail.", __FUNCTION__); return ret; } gpio_direction_output(heater_fan_data->extruder_heater_gpio, HEATER_NOT_WORK); // 挤出机散热风扇 ret = gpio_request(heater_fan_data->extruder_fan_gpio, "ls1c_3dPrinter_heater_fan"); if (0 > ret) { printk(KERN_ERR "[%s] request extruder fan gpio fail.\n", __FUNCTION__); goto fail_request_fan; } gpio_direction_output(heater_fan_data->extruder_fan_gpio, FAN_NOT_WORK); // 初始化挤出机加热的定时器(用于模拟pwm) heater_fan_work_time.extruder_heater_ms = 0; // 加热头不工作 init_timer(&extruder_heater_timer); extruder_heater_timer.function = extruder_heater_timer_timeout_fn; extruder_heater_timer.expires = jiffies + HEATER_FAN_PWM_TIME_MS; add_timer(&extruder_heater_timer); // 初始化挤出机散热风扇的定时器(用于模拟pwm) heater_fan_work_time.extruder_fan_ms = 0; // 风扇不工作 init_timer(&extruder_fan_timer); extruder_fan_timer.function = extruder_fan_timer_timeout_fn; extruder_fan_timer.expires = jiffies + HEATER_FAN_PWM_TIME_MS; add_timer(&extruder_fan_timer); return 0;fail_request_fan: gpio_free(heater_fan_data->extruder_heater_gpio); return ret;}static int heater_fan_remove(struct platform_device *pdev){ gpio_free(heater_fan_data->extruder_heater_gpio); gpio_free(heater_fan_data->extruder_fan_gpio); del_timer(&extruder_heater_timer); del_timer(&extruder_fan_timer); return 0;}static struct platform_driver ls1c_heater_fan_driver = { .driver = { .name = "ls1c_3dPrinter_heater_fan", .owner = THIS_MODULE, }, .probe = heater_fan_probe, .remove = heater_fan_remove,};static int __init heater_fan_init(void){ if (misc_register(&ls1c_heater_fan_miscdev)) { printk(KERN_ERR "could not register 3dPrinter heater fan driver!\n"); return -EBUSY; } return platform_driver_register(&ls1c_heater_fan_driver);}static void __exit heater_fan_exit(void){ misc_deregister(&ls1c_heater_fan_miscdev); platform_driver_unregister(&ls1c_heater_fan_driver);}module_init(heater_fan_init);module_exit(heater_fan_exit);MODULE_AUTHOR("勤为本");MODULE_DESCRIPTION("ls1c 3dprinter heater and fan driver");MODULE_LICENSE("GPL");文件“ls1c_3dprinter_heater_fan.h”放到linux源码目录\include\linux下文件“ls1c_3dprinter_heater_fan.c”放到linux源码目录\drivers\misc下在“linux源码目录\arch\mips\loongson\ls1x\ls1cplatform.c”中，增加#ifdef CONFIG_LS1C_3DPRINTER_HEATER_FAN#include static struct platform_3dprinter_heater_fan_data ls1c_3dPrinter_heater_fan_data = { .extruder_heater_gpio = PRINTER_EXTRUDER_HEATER_PIN, .extruder_fan_gpio = PRINTER_EXTRUDER_FAN_PIN,};static struct platform_device ls1c_3dPrinter_heater_fan = { .name = "ls1c_3dPrinter_heater_fan", .dev = { .platform_data = &ls1c_3dPrinter_heater_fan_data, },};#endif在“static struct platform_device *ls1b_platform_devices[] __initdata”中，添加#ifdef CONFIG_LS1C_3DPRINTER_HEATER_FAN &ls1c_3dPrinter_heater_fan,#endif在“linux源码目录\drivers\misc\Kconfig”中，添加config LS1C_3DPRINTER_HEATER_FAN tristate "ls1c 3dprinter heater and fan" depends on LS1C_MACH help Say Y here if you want to build a 3dprinter heater and fan driver for ls1c 在“linux源码目录\drivers\misc\Makefile”中，添加obj-$(CONFIG_LS1C_3DPRINTER_HEATER_FAN) += ls1c_3dprinter_heater_fan.omake menuconfig Kernel type ---> [*] High Resolution Timer Support Timer frequency (1000 HZ) ---> Device Drivers ---> [*] Misc devices ---> <*> ls1c 3dprinter heater and fan
configuration.h
// 配置头文件#ifndef __CONFIGURATION_H#define __CONFIGURATION_H// Make delta curves from many straight lines (linear interpolation).// This is a trade-off between visible corners (not enough segments)// and processor overload (too many expensive sqrt calls).#define DELTA_SEGMENTS_PER_SECOND 200// NOTE NB all values for DELTA_* values MUST be floating point, so always have a decimal point in them// Center-to-center distance of the holes in the diagonal push rods.// 杆长#define DELTA_DIAGONAL_ROD 220.0 // mm// Horizontal offset from middle of printer to smooth rod center.// 电机轴的圆半径(电机轴组成的等边三角形的最小外接圆的半径)#define DELTA_SMOOTH_ROD_OFFSET 152.0 // mm// Horizontal offset of the universal joints on the end effector.// 装喷嘴的平台的中心到杆连接处的距离#define DELTA_EFFECTOR_OFFSET 35.0 // mm// Horizontal offset of the universal joints on the carriages.//电机轴滑块的距离#define DELTA_CARRIAGE_OFFSET 25.0 // mm// Horizontal distance bridged by diagonal push rods when effector is centered.#define DELTA_RADIUS (DELTA_SMOOTH_ROD_OFFSET-DELTA_EFFECTOR_OFFSET-DELTA_CARRIAGE_OFFSET)// Print surface diameter/2 minus unreachable space (avoid collisions with vertical towers).#define DELTA_PRINTABLE_RADIUS 70// Travel limits after homing (units are in mm)#define X_MIN_POS -DELTA_PRINTABLE_RADIUS#define Y_MIN_POS -DELTA_PRINTABLE_RADIUS#define Z_MIN_POS 0#define X_MAX_POS DELTA_PRINTABLE_RADIUS#define Y_MAX_POS DELTA_PRINTABLE_RADIUS#define Z_MAX_POS 343// 步进电机跑一圈的步数 / 一圈运行的距离// 42步进电机一圈200步，16细分，所以一圈步数=16*200=3200// 步进电机跑一圈运行的距离就需要测了#define DEFAULT_AXIS_STEPS_PER_UNIT {100.0, 100.0, 100.0, 100.0}// pid的取值范围[0,1]#define PID_MAX (1)#define PID_MIN (0)// 虽然理论上，pid值在区间[PID_MIN, PID_MAX]之间都可以// 但pid值太小，开关器件不会动作，等同于为0// 所以当pid值小于此阀值时，直接取0#define PID_ACTION_MIN (0.02)// 加热装置惯性太大，在长时间加热是使用较小的pid值#define PID_LONG_TIME_ACTION (0.4)// pid的调节范围// 当前温度与目标温度的偏差大于该值时，将把pid值设为最大或最小(即全速加热或者不加热)#define PID_FUNCTIONAL_RANGE (5)// 当温度偏差在区间[-PID_FUNCTIONAL_RANGE, PID_FUNCTIONAL_RANGE]内 // 即当前温度在目标温度附近才使用pid算法控温// pid的系数#define DEFUALT_Kp (0.15)#define DEFAULT_Ki (0.0015)#define DEFAULT_Kd (1)#define DEFAULT_Kc (0.0008)// 平滑因子#define PID_SMOOTHING_FACTOR (0.5)#endif temp.c