Magento – Save custom data to custom table error

I need to save data to a custom table.

config.xml

<?xml version="1.0"?>
<config>
    <modules>
        <Npm_Commission>
            <version>0.1.0</version>
        </Npm_Commission>
    </modules>
    <global>
        <events>
            <sales_order_place_after>
                <observers>
                    <npm_commission_model_observer>
                        <type>singleton</type>
                        <class>Npm_Commission_Model_Observer</class>
                        <method>calculateCommission</method>
                    </npm_commission_model_observer>
                </observers>
            </sales_order_place_after>
        </events>
        <models>
            <npm_commission>
                <class>Npm_Commission_Model</class>
                <resourceModel>commission_mysql4</resourceModel>
            </npm_commission>
            <commission_mysql4>
                <class>Npm_Commission_Model_Mysql4</class>
                <entities>
                    <commission>
                        <table>commission</table>
                    </commission>
                </entities>
            </commission_mysql4>
        </models>
        <resources>
            <commission_setup>
                <setup>
                    <module>Npm_Commission</module>
                      <!-- <class>Npm_Commission_Model_Mysql4_Commission</class> -->
                </setup>
                <connection>
                    <use>core_setup</use>
                </connection>
            </commission_setup>
            <commission_write>
                <connection>
                    <use>core_write</use>
                </connection>
            </commission_write>
            <commission_read>
                <connection>
                    <use>core_read</use>
                </connection>
            </commission_read>
        </resources>
    </global>
</config>

DATA

$insertData = array(
            'order_id' => $orderId,
            'transaction_id' => $transaction_id,
            'foundation_id' => $foundation_id,
            'mano_admin_fees' => $manoAdminFees,
            'mano_promotion_fees' => $manoPromoFees,
            'paypal_fees' => $payPalFees,
            'foundation_fees' => $foundationFees,
            'created_at' => $created_at
            );

Insert code

$collectionSet = Mage::getModel('commission/commission');
            $collectionSet->setData($insertData)->save();

custom table install script

<?php
$installer = $this;
$installer->startSetup();
$installer->run("DROP TABLE IF EXISTS {$installer->getTable('commission')};
CREATE TABLE {$installer->getTable('commission')} (
  `id` int(11) unsigned NOT NULL auto_increment,
  `order_id` int(11) NOT NULL,
  `transaction_id` int(11) NOT NULL,
  `foundation_id` int(11) NOT NULL,
  `mano_admin_fees` decimal(10,2) NOT NULL,
  `mano_promotion_fees` decimal(10,2) NOT NULL,
  `paypal_fees` decimal(10,2) NOT NULL,
  `foundation_fees` decimal(10,2),
  `created_at` datetime,
  PRIMARY KEY (`id`)
  ) ENGINE=InnoDB DEFAULT CHARSET=utf8;
");
$installer->endSetup();

I am getting error

Fatal error: Call to a member function setData() on a non-object in