Navigation For Electric Vehicles

This tutorial shows how to make great navigation experience for electric vehicles with navigation session.

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The navigation session leverages the powerful cloud service of Trip Planner for electric vehicles to monitor the remaining battery during navigation. It provides notifications on insufficient battery and a new trip plan if possible.

The navigation session makes a periodic assessment of the remaining battery to make sure that the current charging plan is still valid. The periodic assessment is made every time X% of the available battery at the start of each leg is consumed (X is a configurable value, defaulting to 5, ranging from 2 to 30).

For example:
(with X = 5) 5% battery consumed compared to originally available battery level on each leg - If the available battery on leg departure is 80 KWh, navigation session will make assessments every 4 KWh consumed - If the available battery on leg departure is 30 Kwh, navigation session will make assessments every 1.5 KWh consumed

// adjust percentage of battery consumption to trigger assessment
auto settings = tn::foundation::Settings::Builder()
    .setString(tn::drive::api::SettingConstants::SETTING_NAVIGATION_BATTERY_CONSUMED_CHECK_PERCENT, "10")
    .build();

// create a drive session options with navigation enabled
tn::drive::api::DriveSessionOptions options;
options.enable_navigation = true;

// customized percentage will take effect in all navigation sessions created from this drive session
const auto driveSession = tn::drive::api::DriveSessionFactory::createDriveSession(
    options, system, settings, mapContent, directionService);

If the assessment result is that the remaining battery power is insufficient for the vehicle to reach the next planned charging station (if there's any) or destination (if there's no charging station along the route), a charging station unreachable event will be emitted in the navigation status update.

void NavigationObserver::onNavigationStatusUpdated(const tn::drive::models::v1::NavStatus& navStatus)
{
    const auto& unreachableSignal = navStatus.charging_station_unreachable_signal;
    if (unreachableSignal)
    {
        const auto& batteryLevelInfo = unreachableSignal->battery_level_info;

        // distance from current vehicle location (at the time point when checking) to the predicted location in meters
        // predicted location is upcoming charging station or destination (if there's no upcoming charging station)
        // it's the distance along the route
        const auto distanceToPredictedLocation = batteryLevelInfo.distance_to_predicted_location;

        // estimated travel distance in meters with remaining battery
        const auto estimatedTravelDistance = batteryLevelInfo.estimated_travel_distance;

        assert((distanceToPredictedLocation - estimatedTravelDistance) > std::numeric_limits<float>::epsilon());

        // show warning message about insufficient battery
    }
}

Trip plan for insufficient battery

With the insufficient battery detected, the navigation session will try to make a new trip plan.

void NavigationObserver::onNavigationRouteUpdating(
    const tn::drive::models::v1::BetterRouteUpdateProgress& progress)
{
    // omit other cases...
    else if (reason == tn::drive::models::v1::BetterRouteUpdateProgress::RouteUpdateReason::InsufficientBatteryLevel)
    {
        if (status == tn::drive::models::v1::BetterRouteUpdateProgress::RouteUpdateStatus::Succeeded)
        {
            updateRoute(progress);
        }
        else if (status == tn::drive::models::v1::BetterRouteUpdateProgress::RouteUpdateStatus::Failed)
        {
            // cannot get a new trip plan with the remaining battery
            // get estimated travel distance with remaining battery
            const auto& context = progress.route_update_context;
            const auto& batteryLevelInfo = context.battery_insufficient_info;
            const auto estimatedTravelDistance = batteryLevelInfo.estimated_travel_distance;

            // show warning message for trip plan failure
        }
    }
}

Charing station availability check

Besides the assessment of the remaining battery to reach the next planned charging station, the navigation session will periodically check the availability of the next planned charging station as well. In case it's not available before the vehicle arrives, e.g., all charging facilities are occupied, the navigation session will try to make a new trip plan and propose it to the user.

void NavigationObserver::onBetterRouteDetected(const tn::drive::models::v1::BetterRouteProposal& proposal)
{
    // omit other cases...
    else if (reason == tn::drive::models::v1::BetterRouteProposal::BetterRouteReason::ChargingStationUnavailable)
    {
        const auto& stationInfo = proposal.station_info;

        // entity id of the unavailable charging station
        const auto& stationId = stationInfo.station_id;

        // estimated travel time to the unavailable charging station
        const auto estimatedTravelTime = stationInfo.estimated_travel_time;

        // connector information of the unavailable charging station
        const auto& connectorsInfo = stationInfo.connector_info;

        // show messages about the unavailable charging station
        // and accepts the proposal if user takes it
        navigationSession->acceptRouteProposal(proposal);
    }
}

The availability check of an upcoming planned charging station is triggered if the estimated travel time to it is less than a configurable value. The default time is ten minutes.

// adjust remaining travel time to trigger charging station availability check
auto settings = tn::foundation::Settings::Builder()
    .setString(tn::drive::api::SettingConstants::SETTING_NAVIGATION_CHARGING_STATION_STATUS_CHECK_REMAINING_TIME, "900")
    .build();

// create a drive session options with navigation enabled
tn::drive::api::DriveSessionOptions options;
options.enable_navigation = true;

// customized remaining time will take effect in all navigation sessions created from this drive session
const auto driveSession = tn::drive::api::DriveSessionFactory::createDriveSession(
    options, system, settings, mapContent, directionService);

Navigation For Electric Vehicles