IMU Integration (UBC-Thunderbots#3739)

Author: StarrryNight

src/software/embedded/BUILD

@@ -26,6 +26,7 @@ cc_library(
     deps = [
         ":primitive_executor",
         "//proto:tbots_cc_proto",
+        "//software/embedded/services:imu",
         "//software/embedded/services:motor",
         "//software/embedded/services:power",
         "//software/embedded/services/network",

src/software/embedded/services/BUILD

@@ -31,6 +31,20 @@ cc_library(
     ],
 )
 
+cc_library(
+    name = "imu",
+    srcs = ["imu.cpp"],
+    hdrs = ["imu.h"],
+    deps = [
+        "//proto:tbots_cc_proto",
+        "//shared:constants",
+        "//software/geom:angular_acceleration",
+        "//software/geom:angular_velocity",
+        "//software/logger",
+        "@eigen",
+    ],
+)
+
 cc_binary(
     name = "robot_auto_test",
     srcs = ["robot_auto_test.cpp"],

src/software/embedded/services/imu.cpp

@@ -0,0 +1,316 @@
+#include "imu.h"
+
+#include <fcntl.h>
+#include <linux/i2c-dev.h>
+#include <linux/i2c.h>
+#include <sys/ioctl.h>
+
+#include <climits>  // For SHRT_MAX
+
+#include "shared/constants.h"
+#include "software/logger/logger.h"
+
+// these functions taken from
+// https://git.kernel.org/pub/scm/utils/i2c-tools/i2c-tools.git/tree/lib/smbus.c
+static __s32 i2c_smbus_access(int file, char read_write, __u8 command, int size,
+                              union i2c_smbus_data* data)
+{
+    struct i2c_smbus_ioctl_data args;
+    __s32 err;
+
+    args.read_write = read_write;
+    args.command    = command;
+    args.size       = size;
+    args.data       = data;
+
+    err = ioctl(file, I2C_SMBUS, &args);
+    if (err == -1)
+        err = -errno;
+    return err;
+}
+
+static __s32 i2c_smbus_read_byte_data(int file, __u8 command)
+{
+    union i2c_smbus_data data;
+    int err;
+
+    err = i2c_smbus_access(file, I2C_SMBUS_READ, command, I2C_SMBUS_BYTE_DATA, &data);
+    if (err < 0)
+        return err;
+
+    return 0x0FF & data.byte;
+}
+
+static __s32 i2c_smbus_write_byte_data(int file, __u8 command, __u8 value)
+{
+    union i2c_smbus_data data;
+    data.byte = value;
+    return i2c_smbus_access(file, I2C_SMBUS_WRITE, command, I2C_SMBUS_BYTE_DATA, &data);
+}
+
+
+ImuService::ImuService() : initialized_(false)
+{
+    // Establish connection to the IMU and verify that the who am I pin is correct.
+    file_descriptor_ = open(IMU_DEVICE.c_str(), O_RDWR);
+    int ret          = ioctl(file_descriptor_, I2C_SLAVE_FORCE, 0x6b);
+    if (ret < 0)
+    {
+        LOG(WARNING)
+            << "Failed to initialize the IMU: failed to establish i2c connection.";
+        return;
+    }
+    if (i2c_smbus_read_byte_data(file_descriptor_, WHOAMI_REG) != 106)
+    {
+        LOG(WARNING) << "Failed to initialize the IMU: WHOAMI register "
+                     << static_cast<int>(WHOAMI_REG) << " read incorrectly.";
+        return;
+    }
+    // Attempt to enable gyro and accelerometer, checking that writes are successful
+    // See lsm6dsl datasheet for how to set these registers.
+    i2c_smbus_write_byte_data(file_descriptor_, ACCEL_CONTROL_REG, 0b01000000);
+    if (i2c_smbus_read_byte_data(file_descriptor_, ACCEL_CONTROL_REG) != 0b01000000)
+    {  // write unsuccessful
+        LOG(WARNING)
+            << "Failed to initialize the IMU: writing to accelerometer config register "
+            << static_cast<int>(ACCEL_CONTROL_REG) << " unsuccessful";
+        return;
+    }
+    // Set Gyroscope output data rate to 208 Hz, setting FS to 1000 dps (pg 61 of
+    // datasheet for lsm6dsl, pg 21)
+    i2c_smbus_write_byte_data(file_descriptor_, GYRO_CONTROL_REG, 0b01011000);
+    if (i2c_smbus_read_byte_data(file_descriptor_, GYRO_CONTROL_REG) != 0b01011000)
+    {  // write unsuccessful
+        LOG(WARNING)
+            << "Failed to initialize the IMU: writing to gyroscope config register "
+            << "unsuccessful";
+        return;
+    }
+
+    // Enable Gyro digital LPF1 and set bandwidth to ~65Hz (FTYPE=000)
+    // CTRL4_C: bit 1 (LPF1_SEL_G) = 1
+    i2c_smbus_write_byte_data(file_descriptor_, CTRL4_C, 0b00000010);
+    // CTRL6_C: bits 2:0 (FTYPE) = 000
+    i2c_smbus_write_byte_data(file_descriptor_, CTRL6_C, 0b00000000);
+
+    // Enable Accelerometer digital LPF2
+    // CTRL8_XL: bit 7 (LPF2_XL_EN) = 1
+    i2c_smbus_write_byte_data(file_descriptor_, CTRL8_XL, 0b10000000);
+
+    initialized_ = true;
+    LOG(INFO) << "Initialized IMU! Calibrating...";
+    degrees_error_ = 0;
+    // get 100 sample average of stationary reading, so all future readings can be
+    // corrected
+    double sum        = 0;
+    int valid_samples = 0;
+    for (int i = 0; i < 100; i++)
+    {
+        // Fixed: Call the actual implemented function name
+        auto poll = pollAngularVelocity();
+        if (poll.has_value())
+        {
+            sum += poll->toDegrees();
+            valid_samples++;
+        }
+        usleep(50000);
+    }
+
+    // TODO (3421): More robust calibration
+    if (valid_samples > 0)
+    {
+        degrees_error_ = sum / valid_samples;
+        LOG(INFO) << "IMU Calibration complete. Offset: " << degrees_error_ << " dps";
+    }
+    else
+    {
+        LOG(WARNING) << "IMU Calibration failed: no valid samples received. Angular "
+                        "stability will be poor.";
+        initialized_ = false;
+    }
+
+    // Temporary: enable when need to calibrate
+    // Eigen::Vector2d deviation = calibrate_imu();
+    // LOG(INFO) << "error: " << deviation.x() << deviation.y()  << ".";
+}
+
+std::optional<ImuData> ImuService::poll()
+{
+    std::optional<AngularVelocity> angular_velocity = pollAngularVelocity();
+    std::optional<AngularAcceleration> angular_acceleration =
+        pollAngularAcceleration(angular_velocity);
+    std::optional<Eigen::Vector2d> imu_linear_acceleration = pollLinearAcceleration();
+
+    std::optional<Eigen::Vector2d> linear_acceleration;
+    if (angular_velocity && angular_acceleration && imu_linear_acceleration)
+    {
+        linear_acceleration = transformLinearAcceleration(
+            *angular_velocity, *angular_acceleration, *imu_linear_acceleration);
+    }
+
+
+    return ImuData{angular_velocity, angular_acceleration, linear_acceleration};
+}
+std::optional<int16_t> ImuService::readAndCombineByteData(uint8_t ls_reg, uint8_t ms_reg)
+{
+    int least_significant = i2c_smbus_read_byte_data(file_descriptor_, ls_reg);
+    int most_significant  = i2c_smbus_read_byte_data(file_descriptor_, ms_reg);
+
+    if (least_significant < 0 || most_significant < 0)
+    {
+        return std::nullopt;
+    }
+
+    uint16_t combined = (static_cast<uint8_t>(most_significant) << 8) |
+                        static_cast<uint8_t>(least_significant);
+
+    return static_cast<int16_t>(combined);
+}
+
+std::optional<AngularVelocity> ImuService::pollAngularVelocity()
+{
+    if (!initialized_)
+    {
+        return std::nullopt;
+    }
+
+    std::optional<int16_t> opt_full_word =
+        readAndCombineByteData(GYRO_LEAST_SIG_REG, GYRO_MOST_SIG_REG);
+
+    if (!opt_full_word.has_value())
+    {
+        return std::nullopt;
+    }
+
+    int16_t full_word = opt_full_word.value();
+
+    double degrees_per_sec = static_cast<double>(full_word) /
+                             static_cast<double>(SHRT_MAX) * IMU_FULL_SCALE_DPS;
+
+    return AngularVelocity::fromRadians((degrees_per_sec - degrees_error_) * M_PI / 180);
+}
+
+
+std::optional<AngularAcceleration> ImuService::pollAngularAcceleration(
+    std::optional<AngularVelocity> curr_angular_velocity)
+{
+    if (!initialized_)
+    {
+        return std::nullopt;
+    }
+
+    if (!prev_angular_velocity_.has_value())
+    {
+        prev_angular_velocity_ = pollAngularVelocity();
+        prev_time_             = std::chrono::steady_clock::now();
+        return std::nullopt;
+    }
+
+    auto curr_time = std::chrono::steady_clock::now();
+
+    double dt = std::chrono::duration<double>(curr_time - prev_time_).count();
+    if (dt <= 0 || !curr_angular_velocity.has_value())
+        return std::nullopt;
+
+    double alpha =
+        (curr_angular_velocity->toRadians() - prev_angular_velocity_->toRadians()) / dt;
+
+    prev_angular_velocity_ = curr_angular_velocity;
+    prev_time_             = curr_time;
+
+    return AngularAcceleration::fromRadians(alpha);
+}
+
+
+
+std::optional<Eigen::Vector2d> ImuService::pollLinearAcceleration()
+{
+    if (!initialized_)
+    {
+        return std::nullopt;
+    }
+
+    std::optional<int16_t> opt_x =
+        readAndCombineByteData(ACCEL_X_LEAST_SIG_REG, ACCEL_X_MOST_SIG_REG);
+    std::optional<int16_t> opt_y =
+        readAndCombineByteData(ACCEL_Y_LEAST_SIG_REG, ACCEL_Y_MOST_SIG_REG);
+
+    if (!opt_x.has_value() || !opt_y.has_value())
+    {
+        return std::nullopt;
+    }
+
+    int16_t raw_x = opt_x.value();
+    int16_t raw_y = opt_y.value();
+
+    double a_x = (static_cast<double>(raw_x) / SHRT_MAX) * ACCELEROMETER_FULL_SCALE_G *
+                 ACCELERATION_DUE_TO_GRAVITY_METERS_PER_SECOND_SQUARED;
+
+    double a_y = (static_cast<double>(raw_y) / SHRT_MAX) * ACCELEROMETER_FULL_SCALE_G *
+                 ACCELERATION_DUE_TO_GRAVITY_METERS_PER_SECOND_SQUARED;
+
+    return Eigen::Vector2d(a_x, a_y);
+}
+
+Eigen::Vector2d ImuService::transformLinearAcceleration(AngularVelocity omega,
+                                                        AngularAcceleration alpha,
+                                                        Eigen::Vector2d imu_acceleration)
+{
+    Eigen::Vector2d r(IMU_OFFSET_X, IMU_OFFSET_Y);
+
+    double w = omega.toRadians();
+    double a = alpha.toRadians();
+
+    // tangential: alpha x r → (-alpha*ry, alpha*rx)
+    Eigen::Vector2d tangential(-a * r.y(), a * r.x());
+
+    // centripetal: omega^2 * r
+    Eigen::Vector2d centripetal = (w * w) * r;
+
+    return imu_acceleration + tangential - centripetal;
+}
+
+Eigen::Vector2d ImuService::calibrate_imu()
+{
+    LOG(INFO) << "Start IMU x,y calibration" << std::endl;
+    Eigen::MatrixXd A(2 * 100, 2);
+    Eigen::VectorXd b(2 * 100);
+    int valid = 0;
+
+    for (int i = 0; i < 100; i++)
+    {
+        // Fixed: Call the actual implemented function name
+        auto omega_opt = pollAngularVelocity();
+        if (!omega_opt.has_value())
+        {
+            continue;
+        }
+        auto alpha_opt = pollAngularAcceleration(omega_opt);
+        auto acc       = pollLinearAcceleration();
+        if (omega_opt.has_value() && alpha_opt.has_value() && acc.has_value())
+        {
+            double omega = omega_opt->toRadians();
+            double alpha = alpha_opt->toRadians();
+
+            A(2 * valid, 0)     = -omega * omega;
+            A(2 * valid, 1)     = -alpha;
+            A(2 * valid + 1, 0) = alpha;
+            A(2 * valid + 1, 1) = -omega * omega;
+
+            b(2 * valid)     = acc->x();
+            b(2 * valid + 1) = acc->y();
+            valid++;
+        }
+        usleep(100000);
+    }
+    if (valid < 10)
+    {
+        LOG(WARNING) << "Calibration failed: insufficient valid samples";
+        return Eigen::Vector2d(0.0, 0.0);
+    }
+    Eigen::MatrixXd A_valid = A.topRows(2 * valid);
+    Eigen::VectorXd b_valid = b.topRows(2 * valid);
+    Eigen::Vector2d X =
+        A_valid.bdcSvd(Eigen::ComputeThinU | Eigen::ComputeThinV).solve(b_valid);
+    return X;
+}